A spokesman for the US-led coalition said on Friday that the air strikes in Nuristan province hit militants who earlier attacked a US military base with mortars.

The helicopters identified the militants' firing positions, tracked them down and destroyed the vehicles they were travelling in, said 1st Lt Nathan Perry.

"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. Nuristan's Gov Tamim Nuristani said, however, 22 civilians were killed in the Waygal district of Nuristan province.

"Yesterday afternoon, two civilian vehicles were hit by air strikes," Nuristani said over the phone.

Among those killed were a woman and a child. All 22 dead bodies were brought to a provincial hospital, Nuristani said. Seven other people were wounded. "Last night, the opposition fired rockets at the (US) base and today this incident happened," said Nuristani, speaking from Kabul.

The military base is 9 kilometres away from the place where the airstrike happened, Nuristani said. It was impossible to independently verify any of the claims because of the remoteness of the area.