Attackers are reported to have hit two US military vehicles with grenades and set them ablaze in the Iraqi town of Falluja overnight.
Residents said the US vehicles had come under grenade attack from assailants in a Volkswagen car that drove on. The soldiers opened fire on the surrounding area, they said.
The troops fired back indiscriminately, local residents said. "They were hitting houses and cars," said one man.
One witness said a woman was in hospital as a result of the shooting, but others said there had been no casualties.
But US military spokesmen said they no immediate information on any attack in Falluja, west of Baghdad, where several attacks have been mounted on US troops since about 15 townsfolk were killed in clashes with the Americans in April.