The Islamic State jihadist group has in recent days executed more than 200 members of an Iraqi tribe that fought against it, officials and a tribal leader said on Sunday.
Accounts varied as to the exact period in which the Sunni Albu Nimr tribesmen were killed in various areas of Iraq's Anbar province, but the executions were all said to have been carried out within the last 10 days.
Police Colonel Shaaban al-Obaidi told AFP that there were more than 200 people killed, while Faleh al-Essawi, the deputy head of the Anbar provincial council, put the toll at 258.
The victims, "including women and children, all of them from the Albu Nimr tribe," were killed "during the past three days," Essawi said.
"Anyone who carries the Nimrawi family name on his personal ID" is targeted and killed by IS, he added, referring to the name carried by members of the tribe.
Sheikh Naim al-Kuoud al-Nimrawi, a leader of the tribe, said that 381 of its members were killed "from the 24th of last month until today."
IS has overrun large areas of Anbar, and the killings are likely aimed at discouraging resistance from powerful local tribes, who will be key to any successful bid to retake the province.
Pro-government forces have suffered a string of setbacks in Anbar in recent weeks. That has prompted warnings that the province, which stretches from the borders with Jordan and Saudi Arabia to the western approach to Baghdad, could fall entirely.
Images said to show the aftermath of some of the killings circulated on Twitter, but their authenticity could not be independently confirmed.
One picture that has been circulating in the last week shows a line of more than 30 men in civilian clothes lying in the middle of a street with streams of blood running over the dusty ground, as young men and children look on.
The victims are barefoot and many are blindfolded, their hands bound behind their backs.
IS did not immediately claim responsibility for the killings, but has executed hundreds of people in areas of Iraq and Syria that it controls.
Human Rights Watch says there is evidence the group executed between 560 and 770 men -- mostly captured soldiers --earlier in the year.
IS also executed hundreds of members of a Syrian tribe that fought against them, according to the Syrian Observatory for Human Rights monitoring group.
The sustained bloodshed appears to demonstrate the group's resilience to the U.S. air strikes that have been targeting its fighters in Iraq and Syria.
One leader said he had repeatedly asked the Shi'ite-led central government in Baghdad for arms but that his pleas were ignored.
Albu Nimr had held out for weeks under siege by Islamic State, but finally ran low on ammunition, fuel and food.
Hundreds of tribal fighters withdrew and the tribe fled its main village of Zauiyat albu Nimr, but many were intercepted by the militants who shot them at close range and dumped in mass graves.
Islamic State's advances have fueled sectarian bombings, kidnappings and shootings which occur almost daily in Iraq, echoing the peak of a civil war in 2006-2007.
Also on Saturday, a truck bomb killed 13 people at a vegetable market in the town of Yusufiya just south of Baghdad, police and medical sources said.
In the capital's Doura neighborhood, a bomb killed seven people, including four policemen, security and medical sources said.
In Anbar, fighters have encircled a large air base and the vital Haditha dam on the Euphrates. They also control territory ranging from towns on the Syrian border to parts of provincial capital Ramadi and the lush irrigated rural areas near Baghdad.
Anbar was the main battleground between U.S. Marines and al Qaeda during the "surge" campaign in 2006-2007, when American troops enlisted the help of local tribes, including Albu Nimr.
One leader said the 50 tribe members were killed near Tharthar Lake near a desert area. They had been traveling on foot when they were intercepted by the Sunni militants.
He said one managed to escape the carnage and get word to tribal leaders.
"Forty of the dead were men. Six women and four children were killed while trying to protect their husbands and fathers," said the leader.
His account was confirmed by Faleh al-Essawi, the chief of the security committee of the Anbar Provincial Council.
In the other incident, 35 corpses were found on the outskirts of Ramadi. "They were handcuffed and blindfolded. Some were wearing tracksuits and others were wearing dish-dash robes," an eyewitness told Reuters.
Iraq's Shi'ite Prime Minister Haider al-Abadi wants Sunni tribal leaders to support the Iraqi army against Islamic State, which has threatened to march on Baghdad. But mistrust has undermined efforts to revive an alliance.