"They killed 10 foreign tourists and fled."
Sher said police had not yet established the nationalities of the victims but he had received reports that several were Chinese.
There was no immediate claim of responsibility.
The gunmen fled after the attack, which took place in a remote mountain area at about 1 a.m. on Sunday, Sher said.
A senior government official said a large number of security personnel had been sent to the area.
"Since the area is very remote with no roads or transport, their bodies will have to be retrieved by helicopter," the official said.
Gilgit-Baltistan, which borders China and Kashmir, had been considered one of the more secure areas of Pakistan but has witnessed a spate of attacks by militants targeting members of Pakistan's Shi'ite minority in recent years.
It was the first time foreign tourists had been attacked in the province, which is famous for its natural beauty.