The shooting occurred at a checkpoint manned by soldiers from the US Army's Third Infantry Division at Najaf, 150 kilometers (95 miles) south of Baghad on Monday afternoon, Navy Lieutenant Commander Charles Owens said here.

He said the victims, women and children, were in a vehicle that failed to stop despite repeated warning shots fired by US troops. Four people in the vehicle escaped unharmed.

"As a last resort, they (US troops) fired into the passenger compartment of the vehicle," Owens said at US Central Command's forward planning base here.

"When soldiers opened the vehicle they found 13 women and children inside. Seven of the occupants were dead, two were wounded and four were unharmed."

Owens said an investigation had been opened.