At least eight Afghan soldiers have been killed and five others wounded in what appears to be a US air strike near Kabul, according to the governor of Logar province.

If confirmed, the attack would be the deadliest incident of friendly fire involving international forces since the war began in 2001.

Shortly before 7am on Monday, two helicopters struck an army outpost on a hill in Chiltan, in the district of Baraki Barak in Logar, Mohammad Halim Fidai said.

He could not confirm the origin of the helicopters, but the Logar police chief said they were American. The US military confirmed that its troops had been involved in an incident in the area.