Foreign tourists trapped by heavy fog for six days in the foothills ofMount 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."

Clark said tourists had been kept "in a state of limbo", with little or no information about what authorities were doing to rescue them.

Air traffic control at Lukla's Tenzing-Hillary airport said flights had started again on Monday, with 350 tourists ferried back to Kathmandu by lunch time.

But many gave up waiting for the fog to lift days ago and headed out on foot to Jiri, a four-day walk away, to pick up buses back to Kathmandu.

The army had hoped to deploy its rescue helicopter, which carries up to 40 people, but bad weather has prevented it from accessing Lukla, 135 kilometres (84 miles) from Kathmandu.

A few hundred trekkers have been rescued piecemeal over the last six days by small private helicopters able to carry eight people at a time.

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.

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