Spokesman Ehsanullah Ehsan telephoned AFP to say that the killings were intended to avenge the death of the second in command of the umbrella Tehreek-e-Taliban (TTP) in a US drone strike late last month.
"We did it and we claim responsibility for this attack," Ehsan said in the call from an undisclosed location.
"One of our factions, Junood ul-Hifsa, did it. It is to avenge the killing of Maulvi Wali ur-Rehman," he said.
"We want to convey to the world that this is our reply to US drone attacks," he added.
Rehman died on May 29 in a US drone attack on a house in North Waziristan, the most notorious Taliban and Al-Qaeda stronghold in Pakistan on the Afghan border.
TTP vowed to avenge his death a day later, accusing Pakistan`s government of being responsible for the attack.
Ehsan told AFP that Junood ul-Hifsa was a new wing set up by the Taliban "to attack foreigners and convey a message to the world against drone strikes".
The TTP, a nebulous collection of factions, has been waging a domestic insurgency since July 2007 but is not previously known to have a presence in Gilgit.
Rehman, who had a $5 million bounty on his head, was accused by Washington of organising attacks against US and NATO forces in Afghanistan and also wanted him in connection with a suicide attack on an American base in Afghanistan in 2009 that killed seven CIA agents.
The 42-year-old had been a key figure in the TTP since its inception in 2007 and was second-in-command of the national hierarchy behind Hakimullah Mehsud, as well as leading the group in South Waziristan.
He was seen as a more moderate force than Mehsud and there had been the impression he could have a role to play in possible peace negotiations, but the TTP said it had withdrawn an offer of talks after his death.