At least 10 climbers, including famed Nepali mountaineer Nirmal Purja, were missing on Pakistan's Broad Peak after a suspected avalanche hit an expedition on the mountain, a Pakistani sports association and a person tracking the climb said on Friday.
The 10 climbers are believed to have been swept away by an avalanche on the 8,051-metre (26,414-foot) peak on Thursday, said Chhang Dawa Sherpa, a board director at trekking company Seven Summit Treks (SST).
Broad Peak, the world's 12th-highest mountain, is considered one of Pakistan's most challenging climbs.
SST had three sherpa guides among the missing climbers, Chhang said. Purja, 43, holds the record for the fastest ascent of the world's 14 highest mountains.
The Alpine Club of Pakistan (ACP) said it had "received deeply concerning reports of an avalanche that struck a team of climbers" around midday on Thursday.
Two Pakistan Army Aviation rescue helicopters have been dispatched, the ACP said on Friday, adding that "we remain hopeful for the safe recovery of the missing climbers".
The expedition that was believed to have been struck included Purja and nine other climbers from Nepal, Pakistan, Oman, the US and China, the ACP said.
"The entire team has reportedly been out of communication since the avalanche," it said in a statement on Thursday night.
The government in Pakistan's Gilgit Baltistan region and Pakistan's military media wing did not immediately respond to requests for comment on Friday.
Chhang said team members' last tracked location at the time of the suspected avalanche was at 6,600 metres (21,653 ft) and "fell down straight from there".
Purja first climbed Annapurna, the 10th highest mountain in the world, on April 23, 2019, and then began taking on other "8,000ers."
He became more widely known internationally after a Netflix documentary chronicling his journey was released two years later.
Of the world's 14 highest peaks, eight are in Nepal, five in Pakistan and one in Tibet.
Climbing experts say barely over three dozen mountaineers have climbed all 14 peaks to date.