One of the rescued men, Wilco Van Rooijen, blamed mistakes in preparation for the final ascent - not just the avalanche - for one of mountaineering's worst disasters.
"Everything was going well to Camp Four and on summit attempt everything went wrong," Van Rooijen told The Associated Press by phone from a military hospital, where he was being treated for frostbitten toes.
K2, which lies near Pakistan's northern border with China, is regarded by mountaineers as more challenging to conquer than Mount Everest, the world's highest peak. K2 is steeper, rockier and more prone to sudden, severe weather.
Van Rooijen said several expeditions waited through July for good weather to scale K2 and decided to go for the summit when winds dropped on Friday. 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 28,250-foot peak, including in part a treacherous gully known as 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," said Van Rooijen, 40.
He said those who went on reached the summit just before nightfall. As the fastest climbers descended in darkness across The Bottleneck, about 1,148 feet 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.
Norwegian mountaineer Rolf Bae (far left) and Irish mountaineer Gerard McDonnell are among those missing and presumed dead.
It was not clear how they all died. At least two fell on their way up the mountain, before the avalanche.
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.
The Italian climber, Marco Confortola, descended to 20,340 feet but bad weather forced officials to abort an attempted helicopter rescue Monday, said Qaiser. Confortola, who has made contact by satellite phone and is believed to suffer from frostbite, would continue his descent and another attempt would be made Tuesday, he said.
"Up there it was hell. During the descent, beyond 8,000 meters, due to the altitude and the exhaustion I even fell asleep in the snow and when I woke up I could not figure out where I was," the ANSA news agency quoted the stranded Italian, Marco Confortola, as telling his brother Luigi on the phone.
"My hands are fine, while my feet are black from frostbite. Anyway I can walk and I want to descend to the base camp."
Agostino Da Polenza of Everest-K2-CNR, an Italy-based high-altitude scientific research group, also spoke to Confortola on Monday.
"I never gave up in my life, I am surely not going to give up now," Da Polenza quoted the climber as saying on his group's Web site.
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 16,400 feet, an organizer of their expedition said.
Shahzad Qaiser, a top official at the ministry, said Monday that all climbers who had been caught on K2 during the avalanche were accounted for.
On Monday morning, a helicopter brought Van Rooijen and Dutch colleague Cas Van de Gevel from K2's base camp to a military hospital in Skardu, said Maj. Farooq Firoz, an army spokesman.
Thin air generally prevents choppers from flying above 19,700 feet. The avalanche struck more than 26,250 feet up the mountain.
The reported toll was the highest from a single incident on K2 since at least 1995, when seven climbers perished after being caught in a fierce storm.
Chris Warner, an American who climbed K2 last year, said the Bottleneck gully was the deadliest place on the mountain, with an unstable ice wall above and a fall of up to 9,000 feet below.
"You can see how, for people who were exhausted, it would have been nearly impossible for them to descend without the ropes," said Warner. "Once their hands and feet are frozen, they really are unable to move on their own power, and it takes other people to carry them down."
About 280 people have summited K2 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.