A helicopter has crashed in Nepal, at Everest Base camp, killing two people, both Nepalese, and injuring six others.

Witnesses say the private helicopter was flying low when it slammed into a glacier, not far from a group of tents at the Everest Base Camp. The helicopter was on its way to pick up climbers and take them back to Kathmandu.

An army helicopter ferried the injured to hospitals. A German woman was among the injured.

The Everest Base Camp sits at an altitude of more than 5,500 meters. The thin air and high winds make flying at that altitude dangerous.

There has been a rush of expeditions in recent weeks to Mount Everest to mark the 50th anniversary of the first climb to the summit. An unprecedented 1,000 people are gathered at the Base Camp. More than 130 people have scaled the peak this month.

Veteran mountaineers say the helicopter accident is a stark reminder that conquering the world's highest peak remains dangerous, not only for the climbers, but also for the workers who support their trek.

"This is the great thing that mountaineering and the Himalayas taught me, the value of life," said Indian climber Santosh Yadav, who is the first woman to reach the summit twice. "Because there is [are] certain difficulties," she explained.

The tragedy marred celebrations in the mountain kingdom to mark the Golden Jubilee of the conquest of Mount Everest. Nearly 450 of the 1,200 climbers who have reached the summit are in Kathmandu to join the events. The ceremonies culminate Thursday with a gathering of Everest heroes hosted by Prime Minister Lokendra Bahadur Chand and King Gyanendra.

Wednesday, many mountaineers and their families and friends took time away from the festivities to plant saplings at a memorial park honoring the 175 people who have died trying to scale the world's tallest mountain.

The celebratory mood was also broken briefly by a political protest in Kathmandu. About 20 people were injured when police fired tear gas and used batons to disperse thousands of opposition activists who were marching toward the Parliament. They were protesting King Gyanendra's decision last year to dismiss the elected government, and appoint an interim administration.