ANKARA (Reuters) - U.S. air force jets patrolling Iraq`s northern no-fly zone bombed at least one target on Friday, a U.S. air force official at the jets` home base in Incirlik in southern Turkey said. "At approximately 1.30 p.m. Iraqi time (1030 GMT) U.S. planes responded to Iraqi threats in the northern no-fly zone," Captain Manning Brown told Reuters. He said it was not yet clear how many sites had been hit in the incident. Such strikes have become a regular event since Baghdad announced in December it would actively oppose the no-fly zones in the north and south of Iraq, imposed by the United States and Britain after the 1991 Gulf War. Planes from the Incirlik air base patrol Iraqi skies north of the 36th parallel to protect the area`s Kurdish population from attack by Iraqi President Saddam Hussein`s forces. A similar zone in the south is aimed at protecting the Shi`ites there. Most of northern Iraq is under the control of two Iraqi Kurdish parties which broke away from Baghdad at the end of the Gulf War, but a patch of territory around the city of Mosul remains in the hands of the Iraqi government. The U.S. government says two months of air strikes in the no-fly zones have done more damage to Iraqi air defences than the four days of full-scale attacks on the country in December`s Operation Desert Fox.