Foreign tourists trapped by heavy fog for six days in the foothills of Mount Everest told Monday of their ordeal as they waited to be rescued.

Authorities were forced on Wednesday last week to close the only airstrip in Lukla, the gateway for climbers heading to Everest and surrounding mountains, grounding all flights in and out of the region.

With continuing bad weather hampering a rescue, more than 2,500 trekkers, including Americans, Britons and Germans, have been sleeping at the airport and in tents and dining halls at Lukla hotels, with food fast running out.

"People were anxious and more and more tourists were coming up," said Australian Dicki Clark, 67.

"I was quite frustrated by the fact that nobody knew anything. Our guides were also helpless. They couldn't do anything."

The tourists' ordeal looked to be coming to an end on Monday with the fog lifting, but Clark said they had been kept "in a state of limbo", with little or no information about what authorities were doing to rescue them.

"We are told that we will be flown soon but we can only hope," he told AFP.

Many trekkers gave up waiting for the weather to change days ago and headed out on foot to Jiri, a four-day walk away, to pick up buses back to Kathmandu.

"The weather is clear today and the rescue efforts depend on the weather conditions in coming days," said Mahendra Humagai, an air traffic controller at Lukla's Tenzing-Hillary airport.

"But more tourists are arriving from Everest base camp. So, even if those stranded here are flown to Kathmandu, more are arriving."

The army deployed its rescue helicopter, which carries up to 40 people, for the first time on Monday, after bad weather had prevented it from accessing Lukla, 135 kilometres (84 miles) from Kathmandu.

Tourists told AFP private helicopter firms had been charging up to $6,000 to ferry people out of the area, about twice the going rate.

"It was a free-for-all and there's no government, no organisation to control the crowd," said Chris George, 51, from the United States.

The Nepal Tourism Board said almost 1,000 tourists had been ferried to Kathmandu by late afternoon as airlines began to resume flights.

"As far as I know more than 50 flights were taken between Kathmandu and Lukla to ferry the stranded passengers. The army helicopter also did a few trips," said spokesman Sarad Pradhan.

"Since we don't have any office at Lukla, it has been a very difficult task for us to keep stranded tourists informed about the situation.

"But, through different agencies, we tried our best to keep them safely at Lukla, coordinating with local government agency and local people."

Nepal, a popular destination for mountaineers and trekkers, has eight of the world's 14 tallest peaks over 8,000 metres, including the world's highest, Mount Everest, at 8,848 metres (29,029 feet).

Thousands of foreign tourists visit the Everest region during the peak tourism season late in the year.

Around 500 travellers fly in and out of Lukla on a normal day when weather conditions are good.