BAGHDAD: Militants captured the northern Iraqi town of Tal Afar early on Monday, its mayor and residents said, the latest blow to the nation's Shia-led government a week after it lost a vast swath of territory in the country's north.

The town, with a population of some 200,000 people, mostly ethnic Shia and Sunni Turkomen, was taken just before dawn, Mayor Abdulal Abdoul told The Associated Press.

The ethnic mix of Tal Afar, 420 kilometers (260 miles) northwest of Baghdad, raises the grim specter of large-scale atrocities by Sunni militants of the Al Qaeda-inspired Islamic State of Iraq and the Levant, or ISIL, who already claim to have killed hundreds of Shias in areas they captured last week.

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

The local security force left the town before dawn, said Hadeer al-Abadi, who spoke to the AP as he prepared to head out of town with his family.

Local tribesmen who continued to fight later surrendered to the militants, he said. “Residents are gripped by fear and most of them have already left the town to areas held by Kurdish security forces,” said al-Abadi.

The fall of Tal Afar comes a week after militants captured Iraq's second-largest city, Mosul, and Saddam Hussein's hometown of Tikrit in a lightening offensive. The town is some 150 kilometers (93 miles) from the border with Syria, where ISIL is fighting against President Bashar Assad's government and controls territory abutting the Iraqi border.

The capture of Tal Afar came just hours after Shia Prime Minister Nouri al-Maliki, addressing volunteers joining the security forces, vowed to recapture every inch of territory taken by the militants. “We will march and liberate every inch they defaced, from the country's northernmost point to the southernmost point,” al-Maliki said.

The volunteers responded with Shia chants. Fighting in Tal Afar began on Sunday, with Iraqi government officials saying that ISIL fighters were firing rockets seized from military arms depots in the Mosul area. They said the local garrison suffered heavy casualties and the main hospital was unable to cope with the wounded, without providing exact numbers.

Over the weekend, militants posted graphic photos that appeared to show their gunmen massacring scores of captured Iraqi soldiers. Iraq's chief military spokesman Lt. Gen. Qassim al-Moussawi confirmed the photos' authenticity and said he was aware of cases of mass murder of captured Iraqi soldiers in areas held by ISIL.

He told the AP that an examination of the images by military experts showed that about 170 soldiers were shot to death by the militants after their capture. Captions on the photos showing the soldiers after they were shot say “hundreds have been liquidated,” but the total numbers could not be verified.

US State Department spokeswoman Jen Psaki said the militants' claim of killing the Iraqi troops “is horrifying and a true depiction of the bloodlust that those terrorists represent. “ She added that an ISIL claim that 1,700 were killed could not be confirmed by the US

The grisly images could sap the morale of Iraq's security forces, but they could also heighten sectarian tensions.

Thousands of Shias are already heeding a call from their most revered spiritual leader to take up arms against the Sunni militants who have swept across the north in the worst instability in Iraq since the US withdrawal in 2011.

ISIL has vowed to take the battle to Baghdad and cities farther south housing revered Shia shrines.