"We are constantly trying to make contact with the helicopter. We are trying to reach Kabul but the connection is very bad," an official with Turkmenistan Airlines told AFP.

"We are not dramatising the situation. We hope the situation with our helicopter crew will be resolved favourably," said the official, who asked not to be named.

The official confirmed that the Mi-8 transport helicopter, which had been chartered by the International Committee of the Red Cross (ICRC), had disappeared from radio contact on Saturday after crossing the border from Pakistan into Afghanistan on its way home.

Intense search operations were launched on Saturday and were continuing on Sunday, ICRC spokesman James Reynolds told AFP in Islamabad.

Pakistani security forces were conducting land and air search operations in the areas bordering Afghanistan, while US and NATO forces were combing mountainous areas in Afghanistan, US and NATO officials said in Kabul.

Afghan authorities said they had no information on the missing chopper.

Pakistan was hit by a massive 7.6-magnitude earthquake on October 8 that killed more than 73,000 people in northwestern Pakistan and Pakistani Kashmir, and seriously injured about the same number.