Pakistan on Tuesday declared dead 140 people buried alive by a huge avalanche in a disputed part of the Himalayas more than seven weeks ago.

A huge wall of snow crashed into the remote Siachen Glacier base high in the mountains in disputed Kashmir in the early hours of April 7, smothering an area of one square kilometre (a third of a square mile).

Only three bodies have so far been recovered from the remote glacier, dubbed the world's highest battleground, despite desperate rescue efforts assisted by foreign teams, including from the United States.

The military said that given the improbability of recovering anyone alive, and after consulting religious leaders, "it has been decided to declare the remaining brave soldiers as 'shuhada' (martyrs)" to try to reduce the families' suffering.

"This is being done with mixed feelings of pride, grief and above all unflinching resolve to continue all out efforts to recover the bodies of all shuhada," the military said in a statement posted on its website.

Rescuers have dug tunnels into the mass of snow and ice that hit the battalion headquarters of the 6th Northern Light Infantry to try to recover the bodies of 129 soldiers and 11 civilians at the Gayari camp.

The site is 4,000 metres (13,000 feet) up in the mountains, just below the glacier where Pakistani and Indian troops have faced off since the 1980s.

Kashmir has been the cause of two wars between India and Pakistan and the nuclear-armed rivals fought over Siachen in 1987, though guns on the glacier have largely fallen silent since a peace process began in 2004.