Ammar Al Shamary and Jabeen Bhatti

Special for USA TODAY

BAGHDAD – Islamic militant insurgents captured the northern Iraqi town of Tal Afar early Monday, its mayor and residents said, striking another blow to the nation's Shiite-led government a week after it lost a vast swath of territory in the country's north.

The town has a population of roughly 200,000 people, mostly ethnic Shiite and Sunni Turkomen, and was taken just before dawn, Mayor Abdulal Abdoul told the Associated Press.

A Tal Afar resident reached by phone confirmed the town's fall and said militants in pickup trucks mounted with machineguns and flying black jihadi banners were roaming the streets as gunfire rang out.

The United States said Sunday it was evacuating some staff from its embassy and beefing up security as deadly explosions rocked the Iraqi capital and militants released graphic images appearing to show its fighters massacring captured Iraqi soldiers.

The U.S. State Department said in a statement that an undisclosed number of staffers will be moved to Amman, Jordan, or U.S. consulates elsewhere in Iraq not immediately threatened by the insurgent group, the Islamic State of Iraq and the Levant, or ISIL.

The State Department issued a travel warning for Iraq Sunday night that cautioned U.S. citizens to avoid "all but essential travel to Iraq. Travel within Iraq remains dangerous given the security situation." Violence in many regions of the country is as intense as it's been since 2007, the warning said.

The embassy will remain fully operational with "some additional U.S. government security personnel,'' the State Department said. The embassy, inside the Green Zone near the Tigris River, employs thousands of people, some local hires and others from the United States.

The development came as photos posted on a militant website show what look to be masked fighters of the Islamic State of Iraq and the Levant loading captives onto flatbed trucks before forcing them to lie face-down in a shallow ditch with their arms tied behind their backs. The bodies of the captives are then shown, soaked in blood after being shot.

The AP said the images were verified and were consistent with its reporting. Iraq's top military spokesman, Lt. Gen. Qassim al-Moussawi, confirmed the authenticity of the photos Sunday and said he was aware of cases of mass murder of Iraqi soldiers.

State Department spokeswoman Jen Psaki condemned and denounced as "horrifying" a claim by ISIL that it has massacred 1,700 Shia air force recruits in Tikrit. She called the claim "a true depiction of the bloodlust that these terrorists represent.''

She said that while the United States cannot confirm the massacres, one of the insurgents' goals "is to set fear into the hearts of all Iraqis and drive sectarian division among its people.''

Meanwhile, a string of explosions in Baghdad killed at least 15 and wounded more than 30 on Sunday. A car bomb early Sunday killed 10 and wounded 21 in the city center. After nightfall, another explosion went off in the area, killing two and wounding five. A third blast hit near a falafel shop in the Sadr City district, killing three and wounding seven.

The Wall Street Journal reported that the Obama administration is preparing to open direct talks with Iran on the situation in Iraq and ways to counter the radical Sunni militia there.

Citing an unnamed senior U.S. official, the report said talks could begin this week though no format for discussions has been set.

President Obama, in the desert resort area of Palm Springs, Calif., was briefed on the Iraq situation by National Security Adviser Susan Rice, the White House said.

An embattled city in northwest Iraq, Tal Afar, fell to millitants Sunday, according to Iraqi Gen. Mohammed al-Quraishi, CNN and other media reported.

The Iraqi military earlier had claimed to have repelled an assault by insurgents at Tal Afar, about 30 miles west of Mosul.

"The army with the help of residents of the city managed to stop the attack on the city," said Qassim Atta, spokesman for the Iraqi military.

Military officials said army helicopters destroyed 50 cars full of ISIL fighters Sunday, adding it also killed 279 "terrorists" in the past 24 hours.

Residents who fought against the militants described a chaotic scene.

"The ISIL attacked the town from four directions, but we were ready to fight back," said Mohamad Ahmad, a resident of Tal Afar. "We endured for hours, they came in big numbers, and we fought along with (the) Iraqi army to protect the city."

Tal Afar is a strategic city, and ISIL considers it key to their plan to create an Islamic state spanning Iraq and Syria.

After stunning gains last week including two provincial capitals, Mosul and Tikrit, the advance toward Baghdad was slowed about 30 miles away from the capital with Iraqi commanders saying their forces were now starting to push the militants back and that soldiers had recaptured two towns north of Baghdad.

The crisis prompted Secretary of Defense Chuck Hagel on Saturday to order the aircraft carrier USS George H. W. Bush and two other ships into the Persian Gulf as the U.S. weighs options for responding to the situation as some members of Congress call for airstrikes.

Rep. Mike Rogers, R-Mich., chairman of the House intelligence committee and Sen. Lindsey Graham, R-S.C., argued Sunday on Fox News and CBS, respectively, that the insurgents' success will create a safe haven for planning terrorist activity against the U.S.

While talking on CNN's State of the Union, Graham said the U.S. should engage in talks with Iran to negotiate a settlement in Iraq.

"The Iranians can provide some assets to make sure Baghdad doesn't fall. We need to coordinate with the Iranians," he said.

STORY:Republicans urge U.S. military action in Iraq

In Tikrit, Iraqi troops made their way to a military camp north of the city in an attempt to regroup and retake it. A senior Iraqi officer said they have stopped the movement of militants in the city and are awaiting orders to retake all of Tikrit. He spoke on condition of anonymity because he was not authorized to speak to the news media.

In Mosul, residents reported that life was returning to normal as ISIL removed checkpoints and reopened roads. But residents worried over instructions from militants dictating behavior, saying the directives encroached on their personal freedoms.

"These oblige women to wear loose clothing and only to leave home when absolutely necessary," said Busra Mohammed, 34, a teacher there. "We reject such instructions that want to take us back hundreds of years because they are incompatible with the rights of women and an insult to their dignity."

Contributing: John Bacon, Martha T. Moore, William M. Welch, USA TODAY; Associated Press