The Pakistani ministry of tourism released a list of 11 climbers believed dead: three South Koreans, two Nepalis, two Pakistanis and mountaineers from France, Ireland, Serbia and Norway.
It was not clear how they all died. At least two fell on their way up the mountain, before the avalanche.
All accounted for
Shahzad Qaiser, a senior official at the tourism ministry, said on Monday that all climbers who had been caught on K-2 during the avalanche were accounted for.
An Italian climber, Marco Confortola, made it back to his advanced base camp at 5,400 metres (17,800 feet) on Tuesday.
"I am happy to be alive. I am happy to have gone to the summit of K2, it is something that I've always dreamed of," Confortola said.
Confortola was expected to remain there until Wednesday in order to be evacuated by helicopter.
Van Rooijen's account
"Everything was going well to Camp Four and on summit attempt everything went wrong," Van Rooijen told The Associated Press news agency by phone from a military hospital, where he was being treated for frostbitten toes.
He said several expeditions waited through July for good weather to scale K-2 and decided to go for the summit when winds dropped on Friday.
|The K-2 (Godwin Austin) peak has been the scene of repeated tragedies [AFP]
In all, about two dozen climbers made the ascent, officials said.
But Van Rooijen said advance climbers laid ropes in some of the wrong places on the 28,250ft peak, including in part a treacherous gully known as The Bottleneck.
"We were astonished. We had to move it. That took of course, many, many hours. Some turned back because they did not trust it anymore," he said.
Van Rooijen said those who went on reached the summit just before nightfall. As the fastest climbers descended in darkness across The Bottleneck, about 1,148ft below the summit, a huge serac, or column of ice, fell.
Rooijen said a Norwegian climber and two Nepalese sherpas were swept away.
His own team was split up in the darkness.
Van Rooijen said after the avalanche there was a "whiteout" on the mountain - meaning cloud had descended, making it virtually impossible to see the precipitous route down. But he pushed on as he was starting to suffer snow blindness.
On his descent, he said he passed three South Koreans who had suffered an accident. They declined his offer of help.
"There was a Korean guy hanging upside down. There was a second Korean guy who held him with a rope but he was also in shock and then a third guy was there also, and they were trying to survive but I had also to survive," he said.
It was not immediately clear if they were the same three Koreans who died.
Two other Koreans made it back to the base camp, which lies at about 16,400ft, an organiser of their expedition said.
The reported toll was the highest from a single incident on K-2 since at least 1995, when seven climbers perished after being caught in a fierce storm.
K-2, which lies near Pakistan's northern border with China, is regarded by mountaineers as more challenging to conquer than Everest, the world's highest peak.
K-2 is steeper, rockier and more prone to sudden, severe weather.
About 280 people have reached the summit of K-2 since 1954, when it was first conquered by Italians Achille Compagnoni and Lino Lacedell.
Dozens of deaths have been recorded since 1939, most of them occurring during the descent.