Mourners shout slogans during a funeral in Kirkuk. About 15 Iraqi Turkmen Shiites were killed by militants from ISIS in Tuz Khurmato, according to relatives. (Stringer/Iraq/Reuters)

The villagers lowered 15 bodies into a mass grave here Monday. Two of the dead were young girls. The rest were men. All had been executed at point-blank range by al-Qaeda-inspired rebels and their allies, during what witnesses say was an attack aimed at destroying four Shiite Turkmen communities.

The accounts are among the first to emerge from the villages south of Kirkuk, where residents say a massacre was carried out last week by Sunni fighters with the Islamic State of Iraq and Syria (ISIS) and people who live in nearby Sunni communities.

Human rights groups have expressed horror at a rising tide of sectarian violence in Iraq, including reports from ISIS-controlled areas of beheadings and executions of Shiite religious leaders, civilians and captured security forces. But the residents of the string of Shiite Turkmen villages provided some of the most detailed firsthand accounts of the insurgents’ brutality since ISIS fighters seized control of the northern city of Mosul two weeks ago.

Since then, the insurgents have swept toward the south and west, driving to create a Sunni Muslim nation, governed by Islamic law, stretching across Iraq and Syria. Among those caught in the crosshairs are Iraq’s Turkmens, a minority in this mostly Arab nation, speaking a language that derives from Turkish. While some are Sunni, others are Shiite Muslims — considered apostates by ISIS.

It is not yet clear how many people were killed in the attack on the four farming villages. Gen. Turhan Abdel-Rahman, Kirkuk’s deputy police chief, said he knew of at least 40 slain residents — 25 from three villages who were buried Sunday, plus the 15 interred Monday, who were from the fourth town, Bashir. “There are other bodies still inside Bashir,” he said.

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Scores of people are missing, said more than a dozen residents who spoke to The Washington Post on Monday. Thousands have fled to nearby Shiite communities. The Associated Press first reported on the attack and the expulsions.

The survivors’ stories of civilians being gunned down were reminiscent of the most brutal days of the Iraq war.

The Turkmens have been caught up in past sectarian violence in Kirkuk and other ethnically mixed cities in northern Iraq, but the power of the ISIS rebels adds an explosive new element to such clashes.

Askar Hassan of the Shiite Turkmen village of Brawawchli said the attack began around midday June 17, when many of the town’s residents were napping in the heat. First, shells began to crash into the village. Then he heard gunfire. Hassan grabbed his family and bolted into a nearby field of date palms.

As they ran, a group of men sprayed the fleeing villagers with bullets.

Hassan said he saw his cousin drop from a gunshot before he felt a bullet pierce his own side, sending him to the ground. “Pretend to be dead,” he told his wife and four children as they fell around him. Two of the children had also been shot, he said.

Within moments, the militants had reached them. “God is great!” they shouted, but they moved past his family members, who were lying still, Hassan said.

The family remained on the ground for hours, he said. After nightfall, the militants appeared to have withdrawn, so he and his wife gathered the children and made it back into the town, where they found a car, he said. He said he jump-started it and drove to a nearby hospital. Hassan lifted up his shirt and a bandage to show a reporter the wound from the bullet. His account, and those of other Shiite Turkmens, could not be independently confirmed.

Hundreds of families who escaped the villages of Brawawchli, Karanaz, Chardaghli and Bashir have made it to a Shiite Turkmen neighborhood in Kirkuk, which is under the control of Iraqi Kurdish security forces.

About 400 families — at least a few thousand people — had been “registered” in the neighborhood of Wasiti as of Monday, a self-

appointed organizer for the displaced said, presenting a thick notepad full of names.

“But there are around 4,000 families in all,” said the organizer, Fares Ali Reda. He said he believed that many fled to other areas of Kirkuk and to the nearby town of Tuz Khurmatu. But he couldn’t confirm how many had survived.

Ali, an 18-year-old from Brawawchli, also recalled the shelling that signaled the start of the attack. He said he and other villagers grabbed guns and scrambled onto roofs to fire back at the militants.

“But we didn’t see the snipers” who had approached the town, Ali said. When the bullets started flying amid the shelling, his friend was shot in the neck, said Ali, who gave only his first name. Ali said he ran.

Residents described seeing Humvees and trucks mounted with machine guns and bearing black flags descend on their towns. ISIS rebels have seized Humvees and other equipment from the Iraqi army as they have overrun military positions in the past two weeks.

A few hundred residents of Bashir, most of them men, gathered Monday morning at a cemetery in the neighboring Shiite Turkmen village of Taza. Kurdish security forces and armed Turkmen villagers moved in trucks through the town toward a front line on the outskirts, where they have clashed daily with the Sunni militants.

“They were executed, all shot in the head,” said Abdel-Rahman, who is also head of counterterrorism for the province.

At the cemetery, the mourners gathered around a massive hole, where 15 bodies were lowered into the ground, side by side. The sound of exploding mortar shells reverberated in the distance as a bulldozer shoveled dirt into the grave.

A small group of women cloaked in black, their faces clouded by tears, stood to one side.

The dead girls were sisters, Nargis and Massouma Qassim Ibrahim, ages 10 and 13. “My brother’s girls,” one woman said.

Their father escaped, she said. Their mother and a third sister are missing.

“Please tell the world,” one man said. “It was a savage massacre.”

A local Sunni tribal leader on Sunday had persuaded the jihadists now occupying Bashir to dump the 15 bodies on a road outside the village after they had begun to decompose in the hot sun, relatives said.

A police officer from Bashir, who gave his name as Abu Mustafa, said that on the morning of the assault, local police spotted militants with three pickup trucks laying what appeared to be roadside bombs some distance from the village.

Police officers and villagers engaged the men in a firefight and eventually pushed them several miles down the road, he said.

“On our way back to the village, snipers started shooting at us,” he said. Mortars then began to explode in the town. It was then that police realized the attackers were far more numerous than the men in the three trucks, he said.