US Chinook helicopter 'destroyed'

Chinooks are flying coalition forces in difficult and rugged terrain

An American Chinook helicopter has been destroyed by fire in southeast Afghanistan, US military say.

The incident, which happened late Wednesday, was not caused by hostile fire, the US says.

Coalition forces believe the aircraft caught fire after landing in difficult conditions in Spin Boldak, near the border with Pakistan.

Thirty one people, including six US troops and 25 Afghans, were said to be on board but no one was injured.

The Chinook was one of two conducting an operation in response to reports of insurgent activity in the area.

The aircraft was scheduled to move forces taking part in the operation, US Sergeant Marina Evans said.

Spin Boldak, linking Kandahar with Pakistan's Balochistan province, is near the conflict zone. A team of investigators was due to arrive at the site later on Thursday.

The American military lost another Chinook last month when militants shot down the twin-rotor machine, killing all 17 people on board, in the province of Kunar.