Chopper crashes as US base comes under attack

US Marines in Afghanistan say they have repelled an "almost certain" attack by Taliban forces.

Troops at Camp Rhino went on alert and fired mortars to repel what is believed to be an attempt to probe their defences.

A UH-1N Huey helicopter crashed near the base's airstrip and two servicemen received minor injuries.

Marine spokesman Captain Stewart Upton says one of the injured had been on the ground.

He says the cause of the crash is under investigation, but "we are 99% sure that the helicopter did not crash because of enemy fire".

Before the crash, small arms fire reverberated through the desert base along with the blast of outgoing mortar rounds.

Flares lit up the flat, dusty desert around Camp Rhino while journalists crouched in trenches.

The base went on high alert because of what a spokesman, Captain David Romley, called a "credible threat".

He said armed reconnaissance vehicles were sent into the desert to try to identify the intruders and call in mortar fire.

"We're almost positive it is enemy probing," Upton said. He added that it was clear whoever was moving outside the perimeter had "hostile intent".