The Pakistani Taliban has claimed responsibility for downing a military helicopter, killing six people including the Norwegian and Filipino envoys.

The group said Prime Minister Nawaz Sharif was its target.

"The helicopter was shot down by an anti-aircraft missile, killing pilots and many foreign ambassadors," an Urdu-language statement emailed by its main spokesman Muhammad Khorasani said.

This has not yet been verified, however the region of Gilgit where the crash took place is not known as a stronghold for the militant group.

An earlier statement by Mr Sharif's office had said his plane was en route to the Gilgit area at the time of the attack but turned back to Islamabad after news of the crash broke.

Among the dead are the wives of the ambassadors of Malaysia and Indonesia, the Pakistani army said.

Media said 11 foreigners and six Pakistanis were on board the MI-17, which crashed into a school in Gilgit and caught fire.