The episode began when Afar Ahmed Zidan thought he heard thieves prowling near his home in the darkness, a cousin, Hussain al-Azawi, said. Mr. Zidan went outside and fired at them, Mr. Azawi said.

Image A man cried Wednesday for a dead friend at a house destroyed by an airstrike near Tikrit. Credit... Bassem Daham/Associated Press

But the men in the darkness turned out to be American infantrymen conducting a search, Mr. Azawi said. They returned fire, wounding Mr. Zidan, who rushed inside and frantically called his cousin to alert him to what had happened, Mr. Azawi said. Then the Americans called in an airstrike that killed Mr. Zidan, his wife and three children, all under 10 years old, Mr. Azawi said.

“The Americans shot two rockets into the house,” he said. The rocket strike also wounded three of Mr. Zidan’s neighbors, who were taken to a hospital, he said.

Officials from the local council in Tikrit, about 100 miles north of Baghdad, said Wednesday that they believed five people had been killed in the American airstrike, and that they had sent a representative to attend the funerals.

The American military confirmed an airstrike had taken place, but said an “Al Qaeda terrorist” had fired at the service members. Soldiers surrounded the building where the man was hiding and called for him to come out, the military said, but after perceiving “hostile intent,” they called in the airstrike.

American soldiers and Iraqi police determined that the man had been killed but did not find other victims, the military said. Four women in a neighboring building “sustained only minor injuries,” the military said.

The disputed killings followed a bloody day for American troops elsewhere in Iraq. Three United States soldiers and their interpreter were killed by a roadside bomb in Nineveh Province on Tuesday night, providing more evidence that Sunni Arab guerrillas remain active in Mosul despite recent Iraqi military operations.