Rescuers searching for 138 people buried under a huge avalanche at a Pakistani army camp are concentrating their efforts on five points at the site, the military said on Tuesday.

A huge wall of snow crashed into the remote Siachen Glacier base high in the mountains in Kashmir early Saturday morning, smothering an area of one square kilometre (a third of a square mile).

Experts say there is little chance of finding any survivors at the site, which is at an altitude of around 4,000 metres (13,000 feet).

Despite harsh conditions, the military said efforts had intensified, with more than 450 people taking part -- up from 286 late on Monday -- aided by mechanical earth movers, bulldozers and excavators, and work is focusing on certain key areas.

"Five points have been identified on the site where rescue work is in progress," the military said in a statement.

"Two points are being dug with equipment while three points are being dug manually."

Photographs released by the military Tuesday showed diggers and rescuers at work on an almost featureless expanse of dirty grey snow and ice, with no trace visible of the camp that had been the 6th Northern Light Infantry headquarters.

The total number believed missing in the disaster rose to 138 on Tuesday, as the military released an updated list naming 127 soldiers and 11 civilians. They include a lieutenant colonel, a major and a captain.

Army chief General Ashfaq Kayani visited on Sunday and said an avalanche of this magnitude was unprecedented in the 20 years the battalion had been based at the site.

Manzoor Hussain, the president of the Alpine Club of Pakistan, said the camp had probably been hit by a chunk of glacier that split from the main mass.

He said there was "no possibility" of anyone surviving and warned efforts to find those buried under the mass of snow using specialist equipment would become harder.

"It is becoming difficult to locate people through thermal imagery camera and infra-red system because by now probably there would be no body temperature under the snow," he told AFP.

Retired Pakistani Colonel Sher Khan, a mountaineering expert, suggested the devastation may have been caused by a landslide rather than an avalanche.

"For me it was a huge landslide provoked by a cloud burst, not an avalanche," he told AFP.

"In this case a huge flood of water is coming down from the sky and creates a lot of mud and loose earth on the mountain. Mostly boulders, mud and water ran down the mountain."

Khan said several days of freezing temperatures would have hardened the mass of snow, mud and boulders, making digging more difficult.

Specialist teams from the United States, Switzerland and Germany have arrived in Pakistan to help with the search, though a senior Pakistani security official said the US team has not reached the site due to poor weather.

It is surrounded by some of the world's highest peaks and lies near the de facto border with India in the militarised region of Kashmir, which has caused two of the three wars between the two countries since independence in 1947.

The nuclear-armed rivals fought over Siachen in 1987, but guns on the glacier have largely fallen silent since a slow-moving peace process was launched in 2004.