AN AMERICAN Black Hawk helicopter went down in poor weather in a crash feared to have killed all four on board.
`The helicopter crashed in the Garmsir district of Helmand province on Thursday evening according to Afghan television reports.
A statement from the Nato coalition headquarters in Kabul did not give details of casualties, or survivors, and said the crash site had been secured. The cause of the incident was under investigation, it said.
"We're assuming they're American," an official in Washington told AP.
Helicopters are the main means of military transport in much of the country, allowing troops to avoid roads which are often nearly
impassable for vehicles, or prone to attack with homemade mines.
Crashes occur regularly and the most deadly single incidents for coalition troops have all involved the aircraft either being shot down, or having accidents.
Last month 12 Turkish soldiers and two civilians were killed in a crash on the outskirts of the Afghan capital Kabul.
In January, six US troops were killed in a CH-53 Sea Stallion helicopter crash in the Musa Qala district of Helmand province.
The single deadliest incident for coalition forces during the campaign came in August 2011, when Taliban insurgents shot down a Chinook helicopter in Wardak province, killing 30 Americans and eight Afghans.