Insurgents sent a bloody message on the eve of the 10th anniversary of the U.S.-led invasion, carrying out a wave of bombings across the country Tuesday that killed at least 65 people in the deadliest day in Iraq this year.

The nearly 20 attacks, most of them in and around Baghdad, demonstrated in stark terms how dangerously divided Iraq remains more than a year after American troops withdrew. More than 240 people were reported wounded.

It was Iraq's bloodiest day since Sept. 9, when an onslaught of bombings and shootings killed 92.

Violence has ebbed sharply since the peak of Sunni-Shiite fighting that pushed the country to the brink of civil war in 2006 and 2007. But insurgents are still able to stage high-profile attacks, while sectarian and ethnic rivalries continue to tear at the fabric of national unity.

A woman reacts at the site of a car bomb attack in the Zaafaraniya neighborhood in Baghdad on Tuesday. (Thaier al-Sudani/Reuters)

The symbolism of Tuesday's attacks was strong, coming 10 years to the day that U.S. President George W. Bush announced the start of hostilities against Iraq. It was already early March 20, 2003, in Iraq when the airstrikes began.

The military action quickly ousted Saddam Hussein but led to years of bloodshed as Sunni and Shiite militants battled U.S. forces and each other, leaving nearly 4,500 Americans and more than 100,000 Iraqis dead.

A decade later, Iraq's long-term stability and the strength of its democracy are uncertain. While the country is freer than it was during Saddam's murderous rule, its Shiite-led government is arguably closer to Tehran than to Washington. It faces an outpouring of anger by the Sunni minority that was dominant under Saddam and at the heart of the insurgency that followed his ouster.

"Today's attacks are new proof that the politicians and security officials are a huge failure," said Hussein Abdul-Khaliq, a resident of Baghdad's Shiite slum district of Sadr City, which was hit by three explosions that killed 10 people, including three commuters on a minibus.

The apparently coordinated attacks around the country included car bombs and explosives stuck to the underside of vehicles. They targeted government security forces and mainly Shiite areas.

There was no immediate claim of responsibility, but Iraqi officials believe al-Qaeda's Iraq arm is to blame. The terror group favors car bombs and coordinated bombings to undermine public confidence in the government. It has claimed it was behind two large-scale, well-coordinated attacks already this month, including an assault on the Justice Ministry in downtown Baghdad last week that left 30 dead.

Sabah al-Nuaman, a spokesman for Iraq's counterterrorism services, said al-Qaeda is trying to exploit political instability in the country. He also linked the violence to the civil war across the border in Syria, where largely Sunni rebels — some with ties to al-Qaeda — are trying to topple President Bashar Assad.

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"The terrorist groups are trying to move their operations back to Iraq. They want to make Iraq part of the regional struggle," al-Nuaman said.

The violence started around 8 a.m., when a bomb exploded outside a popular restaurant in Baghdad's Mashtal neighborhood, killing four people, according to police and hospital officials. It blew out the eatery's windows and left several cars mangled in the blood-streaked street.

The deadliest attack was a 10 a.m. car bombing near the Ministry of Labor and Social Affairs in Baghdad's Qahira neighborhood. Seven people were killed.

Another car bomb exploded outside a restaurant near one of the main gates to the fortified Green Zone, which houses major government offices and the U.S. and British embassies. Six people died, including two soldiers. Thick black smoke could be seen rising from the area as ambulances raced to the scene.

At one point amid the chaos, authorities shut bridges spanning the Tigris River in the capital, hoping to thwart further attacks.

Car bombings, roadside blasts, suicide attacks and other mayhem were reported in other parts of the capital as well as in Taji, Tarmiyah, Baqouba and Iskandiriya. In the northern city of Mosul, a local police commander was killed along with two bodyguards by a suicide bomber.

The U.S. and Britain, the two countries that contributed the bulk of the troops for the 2003 war effort, condemned the attacks.

Elections postponed

"The vast majority of Iraqis want to leave behind the violence of the past to build a peaceful and prosperous country," British Foreign Secretary William Hague said in a statement.

Amid the political tensions, Iraq's Cabinet decided Tuesday to postpone next month's local elections in two provinces dominated by Sunnis.

Anti-American Shiite cleric Muqtada al-Sadr blasted the decision and threatened to withdraw his bloc's support from the government.

"Staying in this government has become harmful and not useful at all," he said.