KABUL, Afghanistan - NATO forces killed two insurgents who attacked a police station in northern Afghanistan by hitting their truck with an air strike as they fled, the coalition said Sunday.

Three pickup trucks full of gunmen launched an attack on the main police station in Kunduz province's Aliabad district on Saturday afternoon, said Abdul Rahman Aqtash, deputy provincial police chief.

"They started a gun battle that lasted for about one and half hours," Aqtash said, with police reinforcements and NATO air support called in.

Violence has been on the rise in Kunduz and other northern provinces as the Taliban extend operations beyond their traditional bases in the south.

In a statement, NATO said an air team tracked the insurgents as they drove away, and fired on the truck after determining there were no civilians nearby, the statement said. Several militants were wounded.

In the east, meanwhile, protesters set upon U.S. troops outside of Bagram Air Field, the main U.S. base in the country. A number of people were wounded as the demonstration in Pul-e-Sayad village turned into a riot, NATO said.

The crowd of 250 gathered around the American troops to protest the building of an Afghan army base on land owned by local villagers, said Abdullah Adil, an Interior Ministry official who works with NATO forces in the area.

A few villagers had first gone to the construction site in the morning to demand that work be stopped, and when it was not, they returned with more people, he said.

Protesters threw rocks at the troops as they escorted a contractor to the base, NATO said.

The rocks injured some service members and when they couldn't quell the riot, a soldier fired at the crowd in self-defense, NATO said.

Three Afghans were wounded in the melee, NATO said, without saying who was at fault for the injuries. The troops offered to help the wounded, but locals rejected the assistance, a statement said.

One 12-year-old boy was shot, but his wounds were not life-threatening, Adil said.

Construction has now been halted pending more discussion with the villagers, he said.

"The land dispute is clearly an Afghan government issue that must be settled in order to resolve the ongoing concern of Afghans from the village," Col. William F. Roy said in the NATO statement.