Kurdish forces and Iraqi Arab insurgents exchanged fire yesterday in the latest phase of the battle to control Mosul in northern Iraq.

The Americans and Kurds probed insurgent positions and insurgents launched retaliatory assaults on the Kurds.

The US and Iraqi interim government forces closed the last of five bridges that had remained open since the latest conflict erupted in Mosul a week ago.

American warplanes flew over Arab parts of the city, and some units of the American Task Force Olympia ventured out of their base on patrol. An insurgent unit crossed over to the mainly Kurdish west of Mosul and attacked offices of the Patriotic Union of Kurdistan (PUK). Three of the four attackers were killed, and the fourth was wounded.

The US military said that by mid-afternoon troops had secured several police stations seized by rebels and had met "very little resistance".

Mortars fell near Kurdish positions on the west side of the city. Kurdish gunners on rooftop positions seized last Friday from the militants fired in the direction from which the mortars came. It was impossible to see whether any insurgents were hit.

"The [insurgent] plan was to eliminate the police stations, the Kurdish [party] offices and then the Kurdish community," said Sadi Ahmed Pire, the PUK's representative in Mosul. "The Baath Party worked to create an ethnic war."

Mr Pire and other Kurdish officials claimed that the regrouped Baath Party in Mosul was directing insurgent attacks and that Islamic fundamentalists were, in effect, under Baath Party command. Mr Pire said: "The Baath is in charge. The Islamists are following them."

While he spoke, American jets - having strafed parts of the city last Thursday - roared overhead.

The Americans were forced to dispatch reinforcements to Mosul to quell the attacks by rebels as unrest spread across Iraq after US and Iraqi forces began their offensive against Fallujah.