U.S. troops opened fire on a truck carrying live chickens near the tense town of Fallujah (search), killing five civilians aboard the vehicle, including a father and his two sons, relatives said Wednesday.

The shooting took place at a roadblock Tuesday night, they said. Fallujah (search) is the site of numerous anti-American attacks and U.S. soldiers in the area have been on a high state of alert.

"They went to bring chickens ... and they came back at 9 or 10 at night and we were waiting for them," said Khalid Khalifa al-Jumaily, whose two nephews were killed on the truck. "The Americans fired on them."

On Wednesday, reporters saw U.S. troops delivering one body from an Army ambulance to waiting families. In the morgue, reporters saw several bodies with what appeared to be gunshot wounds.

A spokesman for the U.S. military in Baghdad (search) had no immediate information on the attack.

This weekend, U.S. jets dropped three 500-pound bombs near Fallujah after three U.S. paratroopers were wounded in an ambush.