Updated

An American military tanker refueling plane carrying three crew members crashed Friday in the rugged mountains of Kyrgyzstan, the Central Asian nation where the U.S. operates an air base key to the war in Afghanistan.

There was no immediate word on the fate of the crew. If any of them managed to eject from the KC-135 plane, the search for them would be complicated by the harsh terrain in the region.

The U.S. base in Kyrgyzstan, called the Transit Center at Manas, said it had no immediate information on the cause of the crash, but a resident of the agricultural and sheep-grazing area said the plane exploded in flight.

"I was working with my father in the field, and I heard an explosion. When I looked up at the sky I saw the fire. When it was falling, the plane split into three pieces," Sherikbek Turusbekov said.

The crash site is near Chaldovar, a village about 100 miles west of the base. Pieces of the plane, including its tail, lay in a grassy field bordered by mountains; the air was infused with the heavy stench of petrol.

The base, which is adjacent to the Manas International Airport outside the Kyrgyz capital of Bishkek, was established in late 2001 to support the international military campaign in Afghanistan. It functions as an interim point for troops going into or out of Afghanistan and as a home for the tanker planes that refuel warplanes in flight.

The base has been the subject of a contentious dispute between the United States and its host nation.

In 2009, the U.S. reached an agreement with the Kyrgyz government to use it in return for $60 million a year. But the lease runs out in June 2014, and the U.S. wants to keep it longer to aid in the withdrawal of troops from Afghanistan. Kyrgyzstan is reluctant to extend the lease.

On Monday, a Boeing 747 cargo plane crashed just after takeoff from the U.S. military base in Bagram, Afghanistan, killing all seven people aboard