An American helicopter has crashed in Khost province in southeast Afghanistan, one day after a bomb attack killed 21 people in the province.
Local sources said that the US military helicopter went down in Khost and burst into flames.
There are no words about the possible casualties and the cause of the crash.
But the US-led foreign troops' convoys and aircraft have repeatedly come under fire from the Taliban militants this year.
The US embassy in Afghanistan confirmed on Wednesday that three US-led foreign forces along with their Afghan translator were among the 21 people who were killed on Wednesday.
The casualties came after a bomber riding a motorbike on Wednesday attacked a joint Afghan-NATO convey passing through khost.
The increasing number of troop casualties in Afghanistan has caused widespread anger in the United States and other NATO member states, undermining public support for the US-led war which began in 2001. The offensive removed the Taliban from power, but insecurity continues to rise across Afghanistan, despite the presence of about 130,000 US-led troops.
The US-led war in Afghanistan, with civilian and military casualties at record high, has become the longest military conflict in American history.