Story highlights Elections in two provinces postponed

It is not immediately clear whether all the attacks are related

The attacks come 10 years after the U.S.-led invasion began

Recent attacks in Shiite areas have spread fear among Iraqis

At least 55 people were killed and scores more wounded when bombs exploded across Iraq on Tuesday, a stark reminder of the violence and instability that grips the country 10 years after the start of the U.S.-led war.

The attacks -- 17 car bombs, seven roadside bombs, and two shootings -- ripped mostly through Shiite neighborhoods of Baghdad, but also struck Sunni communities in other towns. At least 187 people were wounded.

The level of carnage has dropped considerably since the height of the sectarian violence in 2006 and 2007 that nearly tore Iraq apart. But the continuing violence serves as a near daily reminder of the violence poses to the fragile political and economic gains in a post-Saddam Hussein Iraq.

Photos: 100 moments from the Iraq War Photos: 100 moments from the Iraq War U.S. Marines in northern Kuwait gear up after receiving orders to cross the Iraqi border on March 20, 2003. It has been more than 10 years since the American-led invasion of Iraq that toppled the regime of Saddam Hussein. Look back at 100 moments from the war and the legacy it left behind. Hide Caption 1 of 100 Photos: 100 moments from the Iraq War A pedestrian looks at front-page headlines on display outside the future site of the Newseum in Washington on March 20, 2003. Hide Caption 2 of 100 Photos: 100 moments from the Iraq War Smoke and flames rise from the riverside presidential palace compound in Baghdad after a massive airstrike on March 21, 2003. Hide Caption 3 of 100 Photos: 100 moments from the Iraq War President George W. Bush meets with his war council in the Situation Room of the White House on March 21, 2003. Clockwise from foreground: National Security Adviser Condoleezza Rice, CIA Director George Tenet, Chief of Staff Andy Card, Secretary of State Colin Powell, Secretary of Defense Donald Rumsfeld and Chairman of the Joint Chiefs of Staff Gen. Richard Myers were present. Hide Caption 4 of 100 Photos: 100 moments from the Iraq War A U.S. Marine from Task Force Tarawa engages Iraqi forces from an armored assault vehicle on March 23, 2003, in the southern city of Nasiriyah. Hide Caption 5 of 100 Photos: 100 moments from the Iraq War Marines walk single-file through the desolate landscape in Nasiriyah on March 26, 2003. As night falls on the city, the troops are on alert for a counterattack. Hide Caption 6 of 100 Photos: 100 moments from the Iraq War A night-vision image shows U.S. military personnel carrying Pfc. Jessica Lynch off a helicopter on April 1, 2003, at an undisclosed location in Iraq. She had been missing since March 23, when she and members of her unit were ambushed by Iraqi forces. Hide Caption 7 of 100 Photos: 100 moments from the Iraq War Members of the 3rd Battalion, 4th Marines, storm Diyala Bridge in Baghdad on April 7, 2003. Hide Caption 8 of 100 Photos: 100 moments from the Iraq War Marines pull down a statue of Saddam Hussein, a symbolic finale to the fall of Baghdad, on April 9, 2003. Hide Caption 9 of 100 Photos: 100 moments from the Iraq War Iraqis flee Baghdad on April 11, 2003, as the capital city descended into chaos with widespread looting and lawlessness. Hide Caption 10 of 100 Photos: 100 moments from the Iraq War Marines hold a memorial service for friends killed in a battle weeks earlier on April 13, 2003, near Al-Kut, Iraq. Hide Caption 11 of 100 Photos: 100 moments from the Iraq War Iraqi National Museum Deputy Director Mushin Hasan sits among destroyed artifacts on April 13, 2003, in Bagdhad. The museum was severely looted. Hide Caption 12 of 100 Photos: 100 moments from the Iraq War Iraqi men push the head of a statue of Saddam Hussein after its destruction on April 18, 2003, in Baghdad. Hide Caption 13 of 100 Photos: 100 moments from the Iraq War Dressed in a flight suit, President Bush meets pilots and crew members of the aircraft carrier USS Abraham Lincoln who were returning to the United States on May 1, 2003, after being deployed in the Gulf region. Hide Caption 14 of 100 Photos: 100 moments from the Iraq War Sailors applaud as President Bush addresses the nation aboard the USS Abraham Lincoln on May 1, 2003. Standing beneath a banner that read "Mission Accomplished," the president declared major fighting over in Iraq and called it a victory in the ongoing war on terrorism. Hide Caption 15 of 100 Photos: 100 moments from the Iraq War A U.S. Marine pulls down a picture of Saddam Hussein at a school in Al-Kut on April 16, 2003. Hide Caption 16 of 100 Photos: 100 moments from the Iraq War Iraqi men check a list near the remains of bodies excavated from a mass grave on the outskirts of Al Musayyib on May 31, 2003. Locals said they uncovered the remains of hundreds of Shiite Muslims allegedly executed by Saddam Hussein's regime after their uprising following the 1991 Gulf War. Hide Caption 17 of 100 Photos: 100 moments from the Iraq War U.S. Army 101st Airborne troops investigate a house where Saddam Hussein's sons Uday and Qusay were killed in Mosul, Iraq, on July 23, 2003. The house, in an affluent neighborhood, was the scene of a fierce gunbattle. Hide Caption 18 of 100 Photos: 100 moments from the Iraq War Army Cpl. Curtis Laymon of the 101st Airborne Rakkasan regiment is reflected in a pool of oil from the Iraqi-Turkey pipeline in Iraq's Ninewa province on October 29, 2003. The pipeline was blown apart by saboteurs two weeks earlier. Hide Caption 19 of 100 Photos: 100 moments from the Iraq War An Iraqi police lieutenant's stars lie in a puddle of blood after a car bombing that targeted a police station in Baquba on November 22, 2003. Hide Caption 20 of 100 Photos: 100 moments from the Iraq War A construction worker removes debris from a destroyed building in Baghdad on December 11, 2003. Hide Caption 21 of 100 Photos: 100 moments from the Iraq War Saddam Hussein's picture is taken December 14, 2003, after his capture a day earlier. U.S. troops found Hussein hiding near his hometown of Tikrit. Hide Caption 22 of 100 Photos: 100 moments from the Iraq War The entrance to the "spider hole" where Saddam Hussein was hiding in Ad Dawr is seen from the inside on December 15, 2003. Hide Caption 23 of 100 Photos: 100 moments from the Iraq War A bound Iraqi informer, with his name inked in English across his back, crouches beside soldiers in the 4th Infantry Division after providing outdated information during a morning raid in in Samarra on December 19, 2003. Hide Caption 24 of 100 Photos: 100 moments from the Iraq War Eman Mohammed, 7, stands in the Kurdish refugee camp in Kirkuk on January 7, 2004. Since 2003, thousands of internally displaced Kurds have returned to Kirkuk. Hide Caption 25 of 100 Photos: 100 moments from the Iraq War Laborers work on a hotel in Baghdad on January 15, 2004. Hide Caption 26 of 100 Photos: 100 moments from the Iraq War A worker turns a valve at the Shirawa oil field outside the northern city of Kirkuk on January 19, 2004. The security of Iraq's oil infrastructure had improved, but exports through the region's main pipeline had yet to resume. Hide Caption 27 of 100 Photos: 100 moments from the Iraq War A boy stands at the scene of a car bombing in front of the Shaheen Hotel in Baghdad on January 28, 2004. Hide Caption 28 of 100 Photos: 100 moments from the Iraq War Mourners carry coffins in Karbala on March 3, 2004. A day after a series of bombs killed dozens and injured hundreds during the Ashura ceremony in the Shiite holy city of Karbala, Shiite Muslims began burying their dead. Hide Caption 29 of 100 Photos: 100 moments from the Iraq War Iraqi insurgents wave their national flag as they celebrate in front of a burning U.S. military tanker they hit with rocket-propelled grenade on April 9, 2004. The attack took place on the road from Baghdad to Fallujah. Hide Caption 30 of 100 Photos: 100 moments from the Iraq War Photographs depicting detainee abuse inside Abu Ghraib prison at the hands of U.S. troops were released in late April 2004. The fallout was immediate, and the images gave anti-war protesters ammunition to rally people to their cause. Hide Caption 31 of 100 Photos: 100 moments from the Iraq War Iraqis look at rows of graves at an overflowing cemetery built in a soccer arena in Fallujah on May 3, 2004. Hide Caption 32 of 100 Photos: 100 moments from the Iraq War At home in Baghdad with his new prosthetic leg, Ahsan Hameed, 20, sits while his aunt looks it over on July 17, 2004. He lost his left leg above the knee to a stray bullet in April. Hide Caption 33 of 100 Photos: 100 moments from the Iraq War Construction workers weld beams at the Ministry of Transportation building in Baghdad on July 21, 2004. The building was being rebuilt after it was gutted by a fire. Hide Caption 34 of 100 Photos: 100 moments from the Iraq War Iraqi national guardsman Ridha Abdulkarim lies in a hospital bed after a car bomb detonated at a checkpoint in Baquba on August 3, 2004. The bomb killed six guardsmen and wounded six others, Iraqi authorities said. Hide Caption 35 of 100 Photos: 100 moments from the Iraq War Shiite militia members prepare to fire during clashes with U.S. forces in Najaf on August 7, 2004. It was the third day of continuous fighting in the holy city. Hide Caption 36 of 100 Photos: 100 moments from the Iraq War An Iraqi militia member injured in a U.S. airstrike in Najaf is assisted by one of his comrades on August 24, 2004. They were walking past the shrine of Imam Ali to make their way to a militia hospital. Hide Caption 37 of 100 Photos: 100 moments from the Iraq War Iraqi Shiite faithful gather in Najaf on August 27, 2004, to mark the end of a battle. Rebel leader Muqtada al-Sadr ordered his fighters to lay down their arms in a peace deal brokered by Iraq's most revered Shiite cleric, Grand Ayatollah Ali al-Sistani. Hide Caption 38 of 100 Photos: 100 moments from the Iraq War Anti-war protesters in New York carry mock coffins draped with U.S. flags on August 29, 2004. Thousands took part in demonstrations outside Madison Square Garden on the eve of the Republican National Convention. Hide Caption 39 of 100 Photos: 100 moments from the Iraq War Members of the Iraqi Intervention Forces listen to last-minute instructions before heading out with U.S. troops to begin a major offensive on the insurgent stronghold of Fallujah on November 8, 2004. Hide Caption 40 of 100 Photos: 100 moments from the Iraq War Marines search houses in Fallujah for insurgents on November 10, 2004. Hide Caption 41 of 100 Photos: 100 moments from the Iraq War Marines rest and check a map in a house during an offensive in Fallujah on November 11, 2004. Hide Caption 42 of 100 Photos: 100 moments from the Iraq War Iraqi men are arrested during a house raid in Fallujah on November 13, 2004. Hide Caption 43 of 100 Photos: 100 moments from the Iraq War Marines take position on a roof in the restive city of Fallujah on November 13, 2004. Hide Caption 44 of 100 Photos: 100 moments from the Iraq War U.S. Army medics treat a wounded Jordanian fighter in Fallujah on November 14, 2004. Hide Caption 45 of 100 Photos: 100 moments from the Iraq War A U.S. Marine and a soldier from the New Iraqi Army process a detainee during operations in Fallujah on November 17, 2004. Hide Caption 46 of 100 Photos: 100 moments from the Iraq War Marines use explosives to open rooftop doors while searching houses in Fallujah for insurgents on November 22, 2004. Hide Caption 47 of 100 Photos: 100 moments from the Iraq War Marines clear a home in Fallujah after four insurgents staged a bloody counterattack, killing one American and wounding many others, on November 23, 2004. Hide Caption 48 of 100 Photos: 100 moments from the Iraq War Spc. Franklin Smith pulls away as a mortar blast is fired from the edge of the U.S. airbase in Tal Afar on January 17, 2005. U.S. teams would frequently fire "harassment and interdiction" mortar fusillades toward suspected enemy positions. Hide Caption 49 of 100 Photos: 100 moments from the Iraq War Iraqis look over their ballots on election day in the Sadr City neighborhood of Baghdad on January 30, 2005. It was the country's first multiparty election in half a century. Hide Caption 50 of 100 Photos: 100 moments from the Iraq War Election officials count ballot papers at night on January 30, 2005, in the Shiite holy city of Najaf. Despite threats, thousands of men and women cast their votes. Hide Caption 51 of 100 Photos: 100 moments from the Iraq War Army Sgt. 1st Class Troy Hawkins is tended to after getting wounded during a firefight while on patrol with an Iraqi army unit in the Haifa Street neighborhood of Baghdad on February 16, 2005. Afterward, he continued to fight in the narrow streets. Hide Caption 52 of 100 Photos: 100 moments from the Iraq War An Iraqi soldier stands watch at a teahouse while on patrol with U.S. soldiers in Baghdad on February 23, 2005. Hide Caption 53 of 100 Photos: 100 moments from the Iraq War President Bush shakes hands with former Sen. Charles Robb, left, and Judge Laurence Silberman during a news conference in Washington on March 31, 2005. The co-chairmen of the Iraqi Intelligence Commission issued a report indicating that U.S. intelligence agencies were wrong in most pre-war assessments about weapons of mass destruction in Iraq. Hide Caption 54 of 100 Photos: 100 moments from the Iraq War Iraqi Shiite demonstrators loyal to cleric Muqtada al-Sadr burn a U.S. flag during a protest in Baghdad on April 9, 2005. The rally was called on the second anniversary of the fall of Baghdad, with protesters demanding an end to the U.S. military presence in Iraq. Hide Caption 55 of 100 Photos: 100 moments from the Iraq War People gather at the scene of a car bombing near a busy market in eastern Baghdad on May, 12, 2005. Hide Caption 56 of 100 Photos: 100 moments from the Iraq War A resident makes a phone call in the aftermath of a double suicide car bombing that struck civilians living near the blast walls that protect the Hamra Hotel in Baghdad on November 18, 2005. Hide Caption 57 of 100 Photos: 100 moments from the Iraq War Sgt. Thomas Gaines kisses his wife during a welcome-home ceremony in Fort Stewart, Georgia, on May 11, 2006. About 280 members of the Georgia National Guard 48th Brigade returned home from a year-long deployment to Iraq. Hide Caption 58 of 100 Photos: 100 moments from the Iraq War A British Royal Air Force gunner waves to a goat herder during a patrol of northern Basra province on July 26, 2006. Hide Caption 59 of 100 Photos: 100 moments from the Iraq War A British armored vehicle is illuminated by traffic during a patrol of Basra on July 27, 2006. Hide Caption 60 of 100 Photos: 100 moments from the Iraq War Ousted Iraqi leader Saddam Hussein addresses the court during his trial in the heavily fortified Green Zone of Baghdad on October 17, 2006. Hussein and six co-defendants were on trial for mass killings in the Anfal campaign against Kurdish rebels in the late 1980s. Hide Caption 61 of 100 Photos: 100 moments from the Iraq War A Palestinian woman watches the news of Saddam Hussein's execution at her home in the West Bank town of Jenin on December 30, 2006. Hussein was hanged for his role in the 1982 Dujail massacre, in which 148 Iraqis were killed after a failed assassination attempt against the then-president. Hide Caption 62 of 100 Photos: 100 moments from the Iraq War U.S. Marines prepare for a military operation at Camp Ramadi in Anbar province on January 14, 2007. Hide Caption 63 of 100 Photos: 100 moments from the Iraq War American forces in Ramadi watch President Bush deliver the annual State of the Union address on January 24, 2007. The president announced plans to increase the size of the U.S. military by 92,000 troops. Hide Caption 64 of 100 Photos: 100 moments from the Iraq War An American Apache helicopter provides air support while a Marine takes aim after being fired upon by insurgents near the Euphrates River in Ramadi on February 2, 2007. Hide Caption 65 of 100 Photos: 100 moments from the Iraq War Iraqi children watch U.S. Army soldiers climb to the roof of their school to get a high vantage point in Baghdad on April 15, 2007. Hide Caption 66 of 100 Photos: 100 moments from the Iraq War U.S. Marines sleep at their patrol base in the area known as Zaidon in Al Anbar province on May 12, 2007. Hide Caption 67 of 100 Photos: 100 moments from the Iraq War Mary McHugh mourns her fiance, Sgt. James Regan, at Arlington National Cemetery in Washington on May 27, 2007. The American Special Forces soldier was killed by an IED in Iraq in February. Hide Caption 68 of 100 Photos: 100 moments from the Iraq War U.S. soldiers and an Iraqi contractor build a concrete wall between Sunni and Shiite areas of the south Dora neighborhood of Bagdhad in the early hours of July 4, 2007. Hide Caption 69 of 100 Photos: 100 moments from the Iraq War Iraqi army commandos teach junior soldiers during a combat training course in Baquba on July 18, 2007. Hide Caption 70 of 100 Photos: 100 moments from the Iraq War Medics treat Army Spc. Jose Callazo after his mine-detecting vehicle hit a buried IED in Hawr Rajab on August 4, 2007. Hide Caption 71 of 100 Photos: 100 moments from the Iraq War An American soldier prepares to search a home for illegal weapons in the Hurriyah neighborhood of Baghdad on September 9, 2007. Hide Caption 72 of 100 Photos: 100 moments from the Iraq War Relatives help an Iraqi man at a hospital in Baghdad on September 20, 2007. He was injured when Blackwater security contractors opened fire on civilians on September 16, killing 17. The company lost its contract to guard U.S. staff in Iraq after the country's government refused to renew its operating license. Hide Caption 73 of 100 Photos: 100 moments from the Iraq War Army Brig. Gen. Nolen V. Bivens presents an American flag to Maribel Ferrero during the funeral of her 23-year-old son, Army Pfc. Marius L. Ferrero, in Miami. He was killed by a roadside bomb while serving in Iraq. Hide Caption 74 of 100 Photos: 100 moments from the Iraq War A U.S. soldier blindfolds an Iraqi man during a raid in Mukhisa on December 3, 2007. Seven men were detained after multiple assault rifles were found in the house. Hide Caption 75 of 100 Photos: 100 moments from the Iraq War U.S. soldiers sit in a home damaged by fighting in Baghdad on March 11, 2008, near the five-year anniversary of the war. Hide Caption 76 of 100 Photos: 100 moments from the Iraq War Commanding Gen. David Petraeus, center, and Ambassador Ryan Crocker testify before the Senate Armed Services Committee in Washington on April 8, 2008. In reporting on the success of the surge in Iraq, Petraeus said the number of U.S. troops in the country should not drop below 140,000. Hide Caption 77 of 100 Photos: 100 moments from the Iraq War A U.S. soldier with 2nd Brigade, 1st Armored Division, stands on a kiln overlooking more than 150 brick factories in Narwan on July 1, 2008. Hide Caption 78 of 100 Photos: 100 moments from the Iraq War A boy looks out from his family shelter at a Narwan brick factory on July 1, 2008. Hide Caption 79 of 100 Photos: 100 moments from the Iraq War Democratic presidential candidate Sen. Barack Obama flies over Baghdad with Gen. David Petraeus during a tour on July 21, 2008. Hide Caption 80 of 100 Photos: 100 moments from the Iraq War Maj. Gen. John Kelly, left, and Anbar province Gov. Maamoun Sami Rashid al-Alwani sign papers during a handover ceremony in Ramadi on September 1, 2008. The U.S. military turned over security control of Iraq's biggest province, once a stronghold of the Sunni insurgency. Hide Caption 81 of 100 Photos: 100 moments from the Iraq War Iraqi Prime Minister Nuri al-Maliki tries to block a shoe thrown at President Bush during a news conference in Baghdad on December 14, 2008. The Iraqi journalist who threw the shoes missed the president but could be heard yelling in Arabic, "This is a farewell ... you dog!" Hide Caption 82 of 100 Photos: 100 moments from the Iraq War Pfc. Jeremy Tomlinson, who was wounded a year before in Iraq, waits with fellow soldiers to greet returning comrades in Fort Carson, Colorado, on January 28, 2008. About 3,800 soldiers were coming home after a 15-month tour of duty. Hide Caption 83 of 100 Photos: 100 moments from the Iraq War A poll worker helps a member of the Iraqi National Police cast his ballot in Baghdad on January 28, 2009. Polls were opened early to members of the Iraqi security services, many of whom would be working during the provincial elections. Hide Caption 84 of 100 Photos: 100 moments from the Iraq War An Iraqi soldier searches a boy at a polling station in Baghdad on January 31, 2009. People across the country voted to fill 440 provincial council seats. Hide Caption 85 of 100 Photos: 100 moments from the Iraq War President Barack Obama delivers an address on February 27, 2009, at the largest Marine post on the East Coast, Camp Lejeune in North Carolina. In his speech, Obama outlined plans for the gradual withdrawal of U.S. troops in Iraq. Hide Caption 86 of 100 Photos: 100 moments from the Iraq War Iraqi army special forces patrol Baghdad's al-Fadel district on March 30, 2009. U.S.-backed Iraqi forces clashed with anti-al-Qaeda militants known as the Awakening Council, or Sahwa, after fighting erupted following the arrest of Adel Mashhadani, a Sahwa leader. Hide Caption 87 of 100 Photos: 100 moments from the Iraq War A U.S. Air Force team carries a flag-draped transfer case containing the remains of Army Spc. Omar M. Albrak of Chicago at Dover Air Force Base in Delaware on May 12, 2009, just over a month after the U.S. government lifted its ban on media coverage of the returning war dead. Albrak was killed while serving in Iraq. Hide Caption 88 of 100 Photos: 100 moments from the Iraq War Army Sgt. Donald Lewis from the 1st Cavalry Division is greeted by his wife, Nicole Lewis, after his brigade arrived home in Fort Hood, Texas, on November 10, 2009, after a year of deployment in Iraq. Hide Caption 89 of 100 Photos: 100 moments from the Iraq War Secretary of Defense Robert Gates speaks with soldiers at a forward operating base in Kirkuk on December 11, 2009. Hide Caption 90 of 100 Photos: 100 moments from the Iraq War An Iraqi woman votes in parliamentary elections in Kirkuk on March 7, 2010. Hide Caption 91 of 100 Photos: 100 moments from the Iraq War U.S. soldiers salute during a handover ceremony of the entry points of Baghdad's Green Zone, now referred to as the International Zone, to Iraqi control inside the heavily fortified compound in Baghdad on June 1, 2010. Hide Caption 92 of 100 Photos: 100 moments from the Iraq War A string of bullets lies across photographs of women adorning the armor of a Stryker vehicle north of Jalaulah on June 11, 2010. Hide Caption 93 of 100 Photos: 100 moments from the Iraq War An Iraqi explosives expert gets into a special suit for bomb disposal during a training session organized by his U.S. counterparts at the Warhorse military base near the restive city of Baquba on August 17, 2010. Hide Caption 94 of 100 Photos: 100 moments from the Iraq War Shiite worshipers pray during an Ashura commemoration ceremony at the Kadhimiya shrine in Baghdad on December 6, 2011. Ashura marks the death of Prophet Mohammed's grandson, the revered Imam Hussein. Hide Caption 95 of 100 Photos: 100 moments from the Iraq War A technician works on a prosthetic at a factory in Baghdad on December 13, 2011. Iraqis have faced a shortage of prosthetics due to a spike in war-related injuries over the years. Hide Caption 96 of 100 Photos: 100 moments from the Iraq War Iraqis gather at a women's art exhibition in a posh Baghdad neighborhood on December 14, 2011. Hide Caption 97 of 100 Photos: 100 moments from the Iraq War Gen. Lloyd Austin retires the United States Forces-Iraq flag during a casing ceremony at the former Sather Air Base in Baghdad on December 15, 2011. Hide Caption 98 of 100 Photos: 100 moments from the Iraq War Military personnel lower their heads during the flag casing ceremony in Baghdad on December 15, 2011. The ceremony officially marked the end of U.S. military operations in Iraq. Hide Caption 99 of 100 Photos: 100 moments from the Iraq War A U.S. soldier prepares to fly out of the Sather Air Base in Baghdad on December 15, 2011. The last U.S. forces left Iraq and entered Kuwait on December 18, nearly nine years after launching a divisive war to oust Saddam Hussein. Hide Caption 100 of 100

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It's the second time in less than a week that the Iraqi capital has endured major simultaneous attacks.

Ten years on, the war left more than 134,000 Iraqis and more than 4,800 U.S. and other coalition service members dead. The war cost hundreds of billions of dollars.

"It remains entrenched and pervasive, with a clear beginning but no foreseeable end, and very much a part of the present in Iraq," said Iraq Body Count, a UK-based group that tracks war deaths.

"In major regions of the country armed violence continues to exact a remorseless toll on human life, young and old, male and female, across society."

In Tuesday's violence, car bombs rocked Baghdad neighborhoods long engulfed in conflict, like Shulaa and Kadhimiya. They struck Mustansiriya University in eastern Baghdad and the fortified International Zone, also known as the Green Zone, where the city's international presence is concentrated. They hit cities north and south of the capital as well. Authorities defused four car bombs in the southern city of Basra.

Attackers set off roadside bombs, another potent weapon for Iraqi insurgents and a defining symbol of the war. One of those bombs rattled Baghdad's teeming Shiite slum of Sadr City.

The U.S. mission in Iraq condemned the attacks in Baghdad and in other provinces -- such as Anbar, Kirkuk, Babel, Nineva, and Diyala.

It was not immediately clear whether the attacks were related. No group immediately claimed responsibility for them.

Ten years later, Iraq is on pins and needles

Change can be seen in the once war-torn nation. A robust form of democracy has taken hold. Sunnis, Shiites, Kurds and others often work together. There is more political, economic and social stability. Coalition forces that ousted Hussein's government have departed.

However, recent attacks in Shiite areas have spread fear among Iraqis that sectarian warfare between Sunnis and Shiites may ravage the country again. Attacks targeting the Justice Ministry last week left 30 dead and 50 wounded in strikes authorities suspect were carried out by al Qaeda in Iraq.

Sunnis had more political clout during Hussein's reign. The Shiites and the Kurds, the other two main groups, were second-class citizens. Since Hussein was toppled, the tables have turned. Shiites -- the largest religious group in the country -- predominate in government. The Kurdish semiautonomous region in the north, and the Kurds themselves, have more clout.

Today, Sunnis feel they've been politically marginalized. They demand that the Shiite-led government stop what they call negative treatment of Iraq's Sunni community.

Sunnis largely boycotted Iraq's 2005 elections, leading to the emergence of a Shiite-led government. The move left the once-ruling minority disaffected.

The deteriorating security situation prompted authorities to postpone provincial council elections scheduled for April in the predominantly Sunni provinces of Anbar and Nineveh.

Expert: The Syrian conflict is hitting home in Iraq

Ramzy Mardini, an expert on Iraq, said the attacks were probably "prescheduled for the anniversary." He also said the latest violence reflects the Sunni-Shiite sectarian tensions raging next door in Syria.

He believes such attacks illustrate the revival of the "capability and confidence" of al Qaeda in Iraq, buoyed by a Syrian uprising "spearheaded by Sunni militancy."

It stands to reason that the attackers are targeting the government of Iraqi Prime Minister Nuri al-Maliki. The Shiite-dominated government is helping neighboring Iran, the largest Shiite nation in the world and a supporter of the Alawite-dominated Syrian government.

"Al Qaeda in Iraq is becoming less exclusive to Iraq. They are trying to channel energy and piggyback off the Syrian revolution by aiming to merge Iraq and Syria into one theater of sectarian war," said Mardini, adjunct fellow at the Iraq Institute for Strategic Studies in Beirut, Lebanon.

"Given that Maliki is helping Iran prop up the Syrian regime, AQI is advertising their cause and looking to attract the support and resources of militant groups in Syria."

Mardini said Sunni militants are baiting al-Maliki and Shiites to retaliate.

"They're working overtime to plunge Iraq back to sectarian war. But more important than the attacks will be how the Shiites respond. Restraint will be key, but harder to achieve should attacks against Shiites continue. Iraq has already entered the electoral season, where everyone on the political scene fuels the fear factor towards their respective sectarian corners."

It is likely that these attacks aren't going to taper off soon, he said.

"What's going on is a campaign, nothing isolated. The Syrian revolution is a strategic force of instability and will continue to provide both rationale and support to Sunnis trying to fight Shiites anywhere in the region," he said. "Growing Sunni discontent directed towards Maliki's government could be providing more cover for al Qaeda fighters to operate than before."

The Obama administration marks the milestone

U.S. President Barack Obama and Secretary of State Chuck Hagel marked the 10th anniversary of the war's beginning with statements praising the service members who fought in Iraq. Obama honored the more than 1.5 million service members and civilians who served there and the memory of the nearly 4,500 Americans who died there.

"The last of our troops left Iraq with their heads held high in 2011, and the United States continues to work with our Iraqi partners to advance our shared interest in security and peace."

Obama said a strong Post-9/11 GI Bill would help veterans pursue jobs and education.

"We must ensure that the more than 30,000 Americans wounded in Iraq receive the care and benefits they deserve and that we continue to improve treatment for traumatic brain injury and post-traumatic stress disorder."

Hagel and Obama also praised the sacrifices of service members' families.

"Our reflections include the Iraqi people -- the Iraqi soldiers and police officers who died alongside our own, the men and women who were caught in the crossfire, and those who still struggle today to secure and govern their nation," Hagel said. "The Iraqi people will determine the future of Iraq and the United States will continue to support their efforts for a peaceful, secure, free, and prosperous nation."