At least nine climbers have perished on K-2, the world’s second highest peak, in Pakistan in one of the blackest days in the sport of mountaineering and the toll could rise, expedition organisers said on Sunday.

Those confirmed dead included three South Koreans, two Nepalese, along with Serbian, Norwegian, Dutch and French climbers.

Unconfirmed reports said one Pakistani had died and several foreign and local climbers were unaccounted for.

Catastrophe struck on Friday, when a chunk of ice broke off from a serac, a pillar or cuboid of ice, and tore away fixed lines from a perilous steep gully known as the Bottleneck, above 8,200 metres (26,902 ft).

Several expeditions were on the mountain, including a Korean team that was making its descent after summiting the 8,611 metre peak, in northern Pakistan near the border with China.

The Korean team lost five members, including the two Nepalese in the ice fall.

’They were returning from the summit when an avalanche at the Bottleneck hit them,’ Ghulam Mohammad, owner of Blue Sky Travels and Tours, told Reuters. ’Our liason officer at the Base Camp confirmed the death of five.’  

Three more fatalities were confirmed by Brigadier Mohammad Akram, vice president of Pakistan’s Adventure Foundation.