An Afghan official says a military helicopter crashed in the country's south, killing 17 people, including five pilots.

Mirwais Noorzai, the chief of police in Zabul province, says the Afghan National Army helicopter crashed in a remote region of the province late Thursday morning.

He says the cause of the crash is unknown and under investigation. He says the other 12 people killed were all soldiers.

The crash is among the worst suffered by the Afghan military since U.S. and NATO forces concluded their combat mission at the end of last year, transitioning to a support and training role.