A rescue helicopter has crashed as it attempted to rescue the survivors of a climbing accident in the American state of Oregon.

Pictures of the helicopter crashing onto a glacier and rolling down a mountainside were seen live on local television.

A horrified television announcer said: "Oh, if only this was a movie."

At least one of the four member crew is thought to be critically injured. The others are in a serious condition.

The Pave Hawk helicopter was part of a rescue effort for nine climbers who had fallen into a crevasse about 245 metres (800 feet) from the summit of Mount Hood, Oregon's highest mountain.

Three climbers died in the fall and at least two others were seriously injured.

The injured climbers and helicopter crew have now been taken to hospitals in Portland.

Risky operation

The exact cause of the crash is still unclear.

The weather was sunny and winds were calm, but officials said any high-altitude helicopter operation is risky.

A paramedic with the group alerted rescue services on his mobile phone.

The helicopter dropped off a rescuer and equipment above the crevasse and then started to lose altitude.

Its refuelling probe got caught in the snow, according to officials - causing the helicopter to career sideways down the mountain.

The rotor blades sheared off and the helicopter rolled over 300m (1,000 ft) before coming to rest.

Cascade mountains

Mount Hood is part of the Cascade mountain range, some 50 miles (80 kilometres) east of Portland, Oregon.

The climbing accident was the second fatal accident this week in the range.

On Wednesday, a man and a woman died in an accident on Mount Rainier, about 60 miles (100 kilometres) from Mount Hood.

The accident came a day after at least two climbers who became trapped in a storm died on Mount Rainier, about 100 miles to the north of Mount Hood.

Mount Hood, the highest peak in the state of Oregon, is the site of one of the worst climbing disasters in the United States.

In May 1986, nine teenagers and two teachers from the Oregon Episcopal School in Portland froze to death while retreating from a storm during an annual climb by students and staff.

In the past 100 years, experts say there have been 130 deaths on Mount Hood.