KABUL, Afghanistan - The U.S. military said today that hostile fire likely brought down a Chinook helicopter that crashed in eastern Afghanistan, and officials said the status of the 17 American servicemembers aboard was "unknown."

If confirmed, Tuesday's attack would apparently be the first time a U.S.-led coalition aircraft here has been downed by hostile fire, representing a major new threat to the coalition. The U.S.-backed mujahideen war against Soviet occupiers in Afghanistan in the 1980s finally turned when the Afghan fighters figured out how to shoot down Soviet aircraft.

The troops were on a mission against al-Qaida fighters when the helicopter went down in mountainous terrain near Asadabad, in Kunar province.

"The helicopter was transporting forces into the area as part of Operation Red Wing, which is part of the enduring fight to defeat al-Qaida militants," a military statement said. "Initial reports indicate the crash may have been caused by hostile fire. The status of the service members is unknown at this time."

U.S. spokeswomen Lt. Cindy Moore said no other details about those on board was available.

Concerns already have been on the rise that rebel attacks here have been escalating into a conflict on the scale of that in Iraq.

More than 660 people have been killed in Afghanistan since March - including 465 suspected insurgents, 29 U.S. troops, 43 Afghan police and soldiers, and 125 civilians - a level unprecedented since the ouster of the Taliban in 2001.

The military statement said coalition and Afghan troops had "quickly moved into position around the crash to block any enemy movement toward or away from the site."

Kunar provincial police chief Abdul Gafar said coalition troops had been dropped by helicopters into the rugged mountains around the crash site.

"This is a tragic event for all of us, and our hearts and prayers go out to the families, loved ones and men still fighting in the area," said U.S. Army Brig. Gen. Greg Champion, deputy commanding general of Combined Joint Task Force-76. "This incident will only further our resolve to defeat the enemies of peace."

Provincial Gov. Asadullah Wafa also told AP that the Taliban downed the aircraft with a rocket.

Purported Taliban spokesman Mullah Latif Hakimi telephoned The Associated Press before news of the crash was released Tuesday and claimed the insurgents shot it down. He said the rebels filmed the attack and would release the video to the media.