U.S. and Iraqi forces killed one fighter, captured another and seized a truck loaded with weapons in an area of northern Iraq that remains an insurgent stronghold, the American military said Monday.

American and Iraqi ground forces backed by a U.S. helicopter attempted to stop a suspicious truck near Tal Abta, about 50 miles west of the volatile city of Mosul, said U.S. military spokesman Maj. Derrick Cheng.

The helicopter came under fire on Sunday and responded with rocket and small arms fire that disabled the truck and killed one of the insurgents, he said.

The American military says Mosul is the last urban battleground of al-Qaida in Iraq and other Sunni extremists, and the level of violence there remains high, even as it has significantly dropped elsewhere in the country.

U.S. and Iraqi forces have carried out many operations in Mosul and surrounding areas as they try to root out Sunni fighters.

U.S. and Iraqi officials have warned that insurgents are trying to spark a conflict between Arabs and Kurds already at deeply at odds over the control of territory.

American forces pulled out from populated areas — including cities, villages and localities — earlier this year according to a security pact with the Iraqi government but still regularly conduct partnered operations with their Iraqi counterparts.

Cheng said gunmen inside the truck fired at the helicopter when U.S. and Iraqi forces attempted to stop the vehicle.

One gunman was able to escape, but a third was captured, and the truck was found to be carrying a load of weapons, Cheng said. He had no further details.

Local police said the man who was detained is believed to be a Yemeni. Cheng confirmed that the prisoner claimed to be a foreigner, but said his nationality is still trying to be confirmed.

Later, in the same area, Iraqi policemen searching for the gunman who escaped clashed with insurgents. Two policemen and two insurgents were killed, a local police officer said. He spoke on condition of anonymity because he was not authorized to speak with the press.