A U.S. military helicopter has crashed in eastern Afghanistan, but the fate of those on board remains unclear.

Military officials say the Chinook helicopter went down Tuesday while transporting troops during a counter-terrorism operation in Kunar province, near the Pakistani border. 

One report says the helicopter was carrying 15 to 20 people.

The military says the cause of the crash was not immediately known. 

In telephone calls to news agencies, a man claiming to speak for the ousted Taleban regime said the rebels have shot down the helicopter.

It was the second crash of a Chinook helicopter in Afghanistan this year.  On April sixth, 15 American servicemen and three U.S. government contractors were killed when their helicopter crashed during a sandstorm in Ghazni province, southwest of Kabul.

Some information for this report provided by AFP and Reuters.