The Pakistan Taliban, an umbrella group of rebel organizations, and a sectarian Sunni group linked to the Taliban claimed responsibility for the killings Saturday of a group preparing to climb Nanga Parbat, the British newspaper The Daily Telegraph reported Monday.
The party included Ukrainian, Chinese and American climbers, as well as their Pakistani guide a statement from the United Nations said.
The Telegraph reported one Chinese climber survived the attack.
The area of the incident, the Gilgit-Baltistan region of Pakistan, was considered among the safer regions in the area, but the attack prompted the British Foreign Office to announce on its website there is "a high threat from terrorism, kidnap and sectarian violence throughout Pakistan."
U.N. Secretary-General Ban Ki-moon condemned the escalating violence in Pakistan, urging the country to "take immediate measures to bring the perpetrators to justice and to ensure security," he said in a statement Monday.