It crashed during an emergency landing in the Gilgit-Baltistan territory.
The wives of the Indonesian and Malaysian envoys and two Pakistani pilots also died. They were to attend the opening of a tourism project.
The Pakistani Taliban (TTP) said they were behind the attack, but there is no confirmation of the claim.
"The helicopter was shot down by an anti-aircraft missile," a statement emailed by Taliban spokesman Muhammad Khorasani said.
However military spokesman Asim Bajwa said on Twitter that the crash had been caused by a technical fault. The area is not a stronghold of the Taliban.
Pakistani Prime Minister Nawaz Sharif was scheduled to attend the inauguration, but his aircraft turned back from Gilgit after reports of the crash.
Bajwa said in an earlier post that Norwegian envoy Leif Larsen and Domingo Lucenario of the Philippines had been killed.
He said five others were injured, including the Polish and Dutch ambassadors.
Eleven foreigners and six Pakistanis were on board the MI-17 helicopter when it came down in the Naltar valley, he added.
'In flames'
The helicopter hit a building belonging to an army school in Gilgit-Baltistan. The building caught fire but no children were in class at the time, a senior official told the AFP news agency.
Local resident Sher Ahmed told the news agency that there had been a heavy security presence in the area ahead of the visit.
"I was in my garden with my family watching the helicopters arriving when we heard a loud explosion and then the school building was in flames."
Meanwhile, an unnamed senior official told Pakistan's Express News that strong winds were blowing when he saw the helicopter crash go down.
The ambassadors of Poland and the Netherlands were among the injured
It was one of three helicopters ferrying a delegation of foreign diplomats for the inauguration of a chairlift project built by the air force for tourists in the area.
The chairlift project was reportedly completed more than six months ago, but its inauguration was delayed due to Prime Minister Sharif's other commitments.
Gilgit-Baltistan is famous for its natural beauty and the main city of Gilgit is seen as a gateway to the Karakoram and Himalayan mountain ranges.
It is also a strategically important autonomous region bordering China, Afghanistan and Indian-held Kashmir.
There have been a number of crashes involving the same model of military helicopter in Pakistan in recent years.
MI-17 helicopter crashes in Pakistan
2012: Five killed in helicopter crash near Skardu airport in Gilgit-Baltistan region
2009: 41 killed in crash in northern Chapri Ferozkhel area
2007: Four killed in crash near Muzaffarabad, the capital of Pakistani-administered Kashmir
2004: 13 killed when helicopter travelling from Rawalpindi to the North Waziristan tribal area crashes
Source: Pakistan's Dawn News
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