Seven members of the team managed to reach camps lower down the mountain.
Survivors included Marco Confortola, an Italian climber, Wilko van Rooiien, a Dutchman, and two Nepali Sherpas, Temba and Cas.
Dren Mandic, the Serbian climber, fell to his death during the ascent and a Pakistani sherpa was also believed to have died last Friday.
Several expeditions were on the mountain.
The head of Italian mountaineering group Ev-K2-CNR said the toll could be higher, according to information he had received from an Italian climber in one of the expeditions.
About a dozen climbers were stranded at the Bottleneck at an altitude known as the Death Zone, because bodies begin degenerating due to the lack of oxygen.
A few were either seen or reported to have made their way back to camps, still high on the mountain.
A Dutch expedition said on its website, noritk2.nl, that three of its team were descending from Camp Three, at 7,350 metres. Two of them were suffering from frostbite.
But it said there was no information about a French climber, Hugues d'Aubarede, Irish climber Gerard McDonnell, and a third climber identified as Karim.
More than 70 climbers have lost their lives on K-2, many of them at the Bottleneck.
Called "the mountain of mountains" by the renowned Italian climber Reinhold Messner, K-2 is not the deadliest in terms of number of fatalities, but statistics show chances of dying making a descent after scaling K-2 are greater than any other peak.