Dozens of Taliban fighters have been killed in US air strikes and a gunbattle in western Afghanistan after an insurgent attack on an Afghan army patrol, NATO and Afghan officials have said.

The Dawn quoted a spokesman of the International Security Assistance Force, as saying that the patrol came under attack in Gulistan district in western Farah province on Wednesday, prompting a call for air support.

"Numerous insurgents were killed, and several motorbikes were damaged or destroyed" following two strikes by coalition aircraft, he said.

Abdul Raoof Ahmadi, a police spokesman in western Afghanistan, said 30 Taliban were killed and another 15 wounded in the fighting in the remote area.

Officials have warned of a hard summer ahead as the fighting season resumes and Afghan national forces assume responsibility of security in more parts of the country from Nato combat forces set to leave by the end of 2014.

Taliban are active in parts of Farah including Gulistan, which falls on a desert highway connecting both Kabul and Kandahar to the western city of Heart.

Mohammed Yunus Rasouli, the Deputy Governor for Farah, said five vehicles of the Afghan national army came under attack when they were crossing Gulistan and three soldiers were burnt inside the vehicle.

"In response, ISAF, the national army and police started a joint operation which still continues," he said, adding he could not give a number of the militants killed.

A Taliban spokesman Qari Yousef Ahmadi said in a text message to reporters that its fighters had killed 40 guards in the attack in Gulistan which he said was carried out on a convoy carrying supplies for foreign troops.