A US military helicopter Sunday crashed in the restive southern Zabul province in south Afghanistan, a US army press release said.

"A US military CH-47 Chinook helicopter crashed southwest of Deh Chopan today," the statement said.

The cause of the crash is unknown at this time, the press release added.

U.S. military ground forces are at the crash scene providing security and recovery operations are ongoing.

The aircraft was supporting operations in the area at the time of the crash.

The mountainous Deh Chopan district in Zabul has been scene of increasing militancy since last year.

Another US military helicopter was crashed in eastern Kunar province late last June killing all 16 on board.

Source: Xinhua