BAGHDAD - Islamic State militants executed at least 220 Iraqis in retaliation against a tribe's opposition to their takeover of territory west of Baghdad, security sources and witnesses said.
Two mass graves were discovered on Thursday containing some of the 300 members of the Sunni Muslim Albu Nimr tribe that Islamic State had seized this week. The captives, men aged between 18 and 55, had been shot at close range, witnesses said.
The bodies of more than 70 Albu Nimr men were dumped near the town of Hit in the Sunni heartland Anbar province, according to witnesses who said most of the victims were members of the police or an anti-Islamic State militia called Sahwa (Awakening).
"Early this morning we found those corpses and we were told by some Islamic State militants that 'those people are from Sahwa, who fought your brothers the Islamic State, and this is the punishment of anybody fighting Islamic State'," a witness said.
The insurgents had ordered men from the tribe to leave their villages and go to Hit, 130 km (80 miles) west of Baghdad, promising them "safe passage", tribal leaders said. They were then seized and shot.
A mass grave near the city of Ramadi, also in Anbar province, contained 150 members of the same tribe, security officials said.
The Awakening militia were established with the encouragement of the United States to fight al Qaeda during the US "surge" offensive of 2006-2007.
Washington, which no longer has ground forces in Iraq but is providing air support, hopes the government can rebuild the shaky alliance with Sunni tribes, particularly in Anbar which is now mostly under the control of Islamic State, a group that follows an ultra-hardline version of Sunni Islam.
But Sunni tribal leaders complain that Shi'ite Prime Minister Haider al-Abadi has failed to deliver on promises of weapons to counter Islamic State's machineguns, sniper rifles, rocket-propelled grenades and tanks.
Sheikh Naeem al-Ga'oud, one of the leaders of the Albu Nimir tribe, said: "The Americans are all talk and no action."
Islamic State was on the march in Anbar this year even before it seized much of northern Iraq in June. As the government and fighters from the autonomous Kurdish region have begun to recapture territory in the north, Islamic State has pressed its advances in Anbar, coming ever closer to Baghdad.