KABUL, Afghanistan - The U.S. military said air strikes by its attack helicopters hit two vehicles carrying insurgents Friday in eastern Afghanistan. Afghan officials said civilians were travelling in the vehicles.

Nathan Perry, a spokesman for the U.S.-led coalition, said the air strikes in Nuristan province hit militants who had earlier attacked a U.S. military base with mortars.

The helicopters identified the militants' firing positions, tracked them down and destroyed the vehicles they were travelling in, he said.

"These were combatants. These were people who were firing on us,'' Perry said. "We have no reports of non-combatant injuries.''

He gave no account of casualties in the vehicles.

Provincial governor Tamim Nuristani said, however, that civilians were travelling in the vehicles in the Waygal district of Nuristan province.

"This afternoon (Friday), two civilian vehicles were hit by airstrikes, and at least six civilians were wounded,'' Nuristani said over the phone.

"Last night, the opposition fired rockets at the (U.S.) base ... and today this incident happened,'' said Nuristani, who was in Kabul at the time.

Mohammad Faruq Khan, a provincial police official, said that over a dozen people were killed or wounded in the strike. He also said airstrikes hit two civilian vehicles in a remote mountainous area.

It was impossible to independently verify any of the claims because of the remoteness of the area.

In other violence, gunmen lobbed a grenade and sprayed a police checkpoint with gunfire in the southern Kandahar province, killing eight officers, said provincial police chief Sumanwal Matiullah.

The attack in Kandahar's Panjwayi district late Thursday also left one officer wounded and two others missing, he said.

The area where the attack occurred is known as a base for Taliban militants.

Police in Afghanistan are frequent targets of Taliban attacks. The under-trained and under-resourced force lost more than 1,000 officers in Taliban attacks last year.

Overall, more than 8,000 people were killed in insurgency-related attacks in Afghanistan last year -- the most since the 2001 U.S.-led invasion. Violence has claimed more than 2,100 lives so far this year.

Elsewhere, a roadside blast next to a police vehicle in central Ghazni province killed two officers and wounded five others, said deputy provincial police chief Mohammad Zaman.

He blamed Taliban militants for the attack.

Meanwhile, in eastern Paktika province, Afghan and foreign troops killed seven suspected militants during a clash near the Pakistan border, said Ghamai Mohammadyar, a spokesman for the provincial governor.

The militants had crossed from Pakistan and attacked Afghan border guards in Bermal district, he said. There were no casualties among Afghan or foreign troops.

Afghan and Western officials say Taliban and other militants regularly use Pakistan's lawless tribal areas as bases for launching attacks against Afghan and foreign troops in the country.

NATO officials say the number of militant attacks have been on the rise this summer, compared with the same period last year.