BAGHDAD — Some of the men were shot on their doorsteps, their bodies left crumpled in the streets. Others were lined up, led to a field and killed there. Their relatives, ordered to stay in their homes, heard the gunfire.

At least 72 people from a majority Sunni village in eastern Iraq were methodically singled out for slaughter this week, according to witnesses and local Sunni leaders, who said the victims were killed by Shiite militiamen who were supporting Iraqi security forces.

A spokesman for Iraq’s prime minister said Thursday that the government was investigating the claims. Some local security officials in Diyala Province have asserted the victims were militants killed in battle by the security forces, denying that sectarian executions had occurred.

But witness accounts suggest that is what happened in the village of Barwanah starting on Monday. Several survivors described seeing a column of troops drive into the village that afternoon, quickly followed by a convoy of militia fighters. The militiamen started calling out specific names of people they were seeking, then began killing.