ISLAMABAD, Pakistan  At least nine climbers were reported dead on Sunday on K-2, the world’s second highest mountain, after an avalanche struck them on a steep gully at a height of nearly 27,000 feet, just below the summit.

Those who perished included South Koreans and Nepalese, the Pakistani television station ARY reported. Serbian, Norwegian, Dutch and French climbers were also believed to be among those who might have died, according to ARY. Other climbers are feared to be missing.

The death toll appears to be the largest ever on K-2.

The accident occurred when a chunk of ice from an ice pillar snapped on Friday, breaking fixed ropes on the area of the peak, just below the summit, known as the Bottleneck, according to expedition organizers. A team of South Korean climbers were on their way down from the summit, according to Ghulam Mohammad, the owner of Blue Sky Travels and Tours. He said five members of the Korean team perished and two Nepalese died. The nationalities of the others who died was not clear.

Several expeditions were on the mountain over the weekend, and some reports said about a dozen climbers were stranded at Bottleneck, a region known as the “Death Zone” because bodies begin degenerating from lack of oxygen. Climbers stuck above Bottleneck would be unable to descend because of the broken ropes, according to expedition organizers.