Afghanistan's Ministry of Defense says five soldiers and a police officer were killed in an air strike carried out by an Afghan military helicopter in western Farah province.

The ministry said in a statement Saturday the helicopter had used "inaccurate information from ground forces" when it conducted the air strike late Friday night.

It says the forces were being attacked by insurgents in the Bala Buluk district. When they called for air support, the helicopter incorrectly fired a rocket at a checkpoint occupied by Afghan security forces.

The incident is being investigated, the statement says.

It comes after a U.S. air strike in eastern Nangarhar province early Wednesday killed at least 15 people. Officials and the U.N. mission in Kabul say the dead were civilians.