Nazir Sabir says 22 climbers, mostly foreigners, reached K-2's summit Saturday but an ice avalanche struck them during their descent.
He says nine of the mountaineers are feared to have died and three others are missing. His Alpine Club of Pakistan organized a Serbian expedition on the mountain.
Sabir says a Serbian climber is among the nine feared dead.
K-2 is 28,250 feet tall, about 785 feet shorter than the world's highest peak, Mount Everest. But climbers generally regard K-2 as a more difficult peak to conquer.