Iran blamed the US for the ambush, saying Washington's threats against it encourage terrorist attacks against Iranian interests in Iraq.

"The suspicious behavior of US forces in security issues has brought increasing insecurity in Iraq," Mohammad Ali Hosseini, an Iranian foreign ministry spokesman, said in a statement, a copy of which was made available to the Associated Press news agency.

"Responsibility for providing security to diplomats as well as diplomatic and international bodies in Iraq rests with the occupiers."

Hosseini said threatening statements by US authorities against Iran were only encouraging fighters to carry out terror attacks.