Prime Minister Nawaz Sharif was in a separate plane and returned to Islamabad when news of the crash broke

The ambassadors for Norway and the Philippines were among six people killed today after a helicopter crashed onto a school in northern Pakistan - with the Taliban claiming they downed it as part of a plot to kill Prime Minister Nawaz Sharif.

Leif H. Larsen, the Norwegian envoy, and Domingo D. Lucenario Jr, of the Philippines, were killed along with the wives of the Malaysian and Indonesian ambassadors, as well as the helicopter's two pilots.

The Pakistani Taliban issued a statement claiming they had shot down the helicopter with an anti-aircraft missile - but the army have denied this, and indicated the cause was a technical fault.

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Six people have died today after a Pakistani army helicopter crashed into the Naltar Snow School, which was closed, in northern Pakistan

Leif H. Larsen (pictured left), the Norwegian envoy, and Domingo D. Lucenario Jr (right), of the Philippines, were killed in today's crash in Pakistan

'A special group of Tehreek-e-Taliban Pakistan had prepared a special plan to target Nawaz Sharif during his visit but he survived because he was travelling in another helicopter,' militant spokesman Muhammad Khorasani said.

It was not immediately possible to verify the Taliban claim and the northern region where the chopper came down, Gilgit-Baltistan, is not known as a stronghold of the militant organisation.

The helicopter, carrying 17 passengers, fell onto the Naltar Snow School and set the building ablaze, the Express Tribune reported.

Officials clarified the school was shut at the time.

Prime Minister Nawaz Sharif was travelling in a plane to the mountainous northern region of Gilgit at the time of the incident, but turned back to Islamabad after news of the crash broke.

He was due to attend a public ceremony to inaugurate a newly installed chair-lift at a ski resort.

In his statement, he expressed his 'deep grief and sorrow over the tragic incident' and said he 'extended heartfelt condolences to those who lost their lives in this incident.'

The wives of the Malaysian and Indonesian ambassadors, as well as the helicopter's two pilots, also died

Air Chief Marshal Sohail Aman, of Pakistan Air Force, visits the Malaysian Ambassador Hasrul Sani Mujtabar at the CMH hospital in Gilgit, Pakistan

The ambassadors of Norway and the Philippines were among six people killed in a helicopter crash in Pakistan. Pictured, soldiers next to an army helicopter at a military hospital where victims are being treated

The helicopter crashed into a school near the town of Gilgit as children attended classes and caught fire. Pictured, Pakistani soldiers stand guard outside a military hospital in Gilgit

Asim Bajwa, Pakistan's army spokesman, announced on Twitter that the MI-17 helicopter made the emergency landing in the northern region of Naltar

The Pakistani military helicopter had been carrying 11 foreigners and six Pakistanis when it made a crash landing, hitting a school near the town of Gilgit and killing two pilots and four foreign passengers.

Norway has expressed 'great sadness' over the death of its ambassador to Pakistan.

Leif Larsen, 61, was 'one of our best and most experienced diplomats' who was 'very respected by his colleagues,' said Foreign Minister Borge Brende.

The Pakistani Taliban claimed responsibility and said Prime Minister Nawaz Sharif had been the target. The claim has not been verified

Officials warned the situation was 'urgent' after the helicopter - one of three taking a delegation of foreign diplomats and their aides - crashed into the school and caught fire.

Asim Bajwa, Pakistan's army spokesman, the MI-17 helicopter made the emergency landing in the northern area of Naltar.

He tweeted: 'Update Naltar: info so far; two pilots and two-three foreigners fatalities. Thirteen survivors with varying degree of injuries.'

He added Andrzej Ananiczolish, the ambassadors of Poland, and Dutch ambassador Marcel de Vink were among the injured.

Local media reports say the ambassadors of Romania and Lebanon have been injured as well as the high commissioners of South Africa and Indonesia.

The convoy of three helicopters was carrying a delegation of foreign diplomats and their aides to Pakistan's Gilgit-Baltistan territory, which is part of the disputed Kashmir region.

'It was a diplomatic trip with members of 37 countries in total,' said a passenger in one of the helicopters, who asked not to be named, adding that the school had caught fire after the crash.

'We have been told to send in as many ambulances as we can because the situation there is 'urgent',' said a senior official.

The injured were being air lifted to a military hospital in Gilgit, the region's administrative capital, some 50 kilometres (30 miles) to the southwest, added another senior local police official.

In the city of Gilgit, a hospital official said injured were being carried on stretchers to the emergency ward of the Combined Military Hospital.

The flag at the Embassy of Norway in Islamabad, Pakistan, was lowered to at half-mast after the death of Ambassador Leif Larsen today