KABUL: An Afghan air force strike killed five soldiers and a police officer in western Afghanistan, an official said Saturday, the latest in a series of so-called “friendly fire” incidents.

Afghan helicopters “mistakenly” bombed their own forces after calling in air support as they battled the Taliban in the Kensk area of Farah province late Friday, Dawlat Waziri, a defense ministry spokesman, said.

“Because of the wrong coordinates, helicopters bombed an Afghan forces' checkpoint that unfortunately left five soldiers and one police officers dead,” he said.

“An investigation into the incident has been launched,” he added.

Last month a US air raid killed eight Afghan policemen in the southern province of Uruzgan, in the first such incident since American forces were given greater powers to strike at insurgents.

The US military in Afghanistan, however, said its forces were not involved in the air strike in Farah.

Civilian and military casualties caused by NATO and Afghan forces have been one of the most contentious issues in the 15-year campaign against Taliban insurgents, prompting harsh public and government criticism.

A US air strike killed up to 10 Afghan soldiers in July last year at an army checkpoint in Logar province south of Kabul, one of the deadliest episodes of “friendly fire” by foreign forces in recent years.

Afghanistan has a tiny air force compared to NATO's fleet, which carried out supply operations, air strikes and emergency evacuations until the drawdown of foreign coalition forces in 2014.

The air force has recently began bombing Taliban militants as the fighting rages in several provinces across the country.