Witnesses on Tuesday said heavy clashes broke out in Karma after fighters attacked a US military convoy using mortars, rocket-propelled grenades and automatic weapons. 

They said at least two US military vehicles had been damaged and troops had cordoned off the area, but it was not clear whether there were any US casualties. 

The US military had no immediate comment. 

Ahmad Ghani, a doctor at Falluja's main hospital, said 11 Iraqis had been killed and more than 20 wounded. A call was put out for locals to donate blood to help the wounded.