The Afghan defence ministry also ordered the nation's air force to be on standby.

Offcials said there was no immediate word on the passengers' fate, who included six foreigners.

The British embassy in Kabul confirmed that three UK citizens were on the aircraft, but did not identify them.

One American also was on board, a state department official in Washington said on condition of anonymity pending notification of family.

The nationalities of the two other foreigners were not immediately available.

'Conditions bad'

Al Jazeera's Hoda Abdel-Hamid, reporting from Kabul, said: "The conditions are bad. It's so foggy there is no rescue going on.

Referring to the Nato force in Afghanistan - the International Security Assistance Force - she said: "Two Isaf helicopters are en route to the area. Other Isaf helicopters are also on standby ... to assist in any rescue effort."

Colonel Nabiullah, who is in charge of the southern portion of the Salang Pass, said: "The only way they can search is on foot. The helicopters can't get in."

Afghanistan's acting transport minister said the cause of the accident was not yet known.
"We have to recover the black box to determine the cause," Mohammadullah Bataz said.
"We cannot rule out any of the usual causes behind crashes; which could be bad weather, technical error, thunder and lightning or even terrorist attacks."

Other officials blamed the weather for the crash.

Pamir Airways is one of three major private airlines that operate mostly domestic routes across Afghanistan.

It has daily flights to major Afghan cities and also operates flights to Dubai and Saudi Arabia for the Haj pilgrimage.

According to its website, it uses Antonov An-24 type aircraft on all its Kunduz-to-Kabul flights.