Pakistan Army helicopters embarked on a "search flight" on Saturday but returned to Skardu after they were unable to locate three climbers, including Pakistan's Muhammad Ali Sadpara, who went missing while attempting to summit the world's second-highest mountain, K2.

Sadpara, John Snorri from Iceland and JP Mohr from Chile have not been contacted since the three began their push for the K2 summit from camp 3 at midnight between Thursday and Friday, according to their team.

News of the missing men comes a day after a Bulgarian mountaineer was confirmed to have died on K2.

At the time the three began their summit attempt, 18 members of one of the expedition teams decided to abandon their attempt and spent the night at camp 3, choosing instead to descend on Friday morning.

According to the Alpine Club, two Pakistan Army helicopters started a search and rescue mission on Saturday at 11am to locate the three missing climbers who at the time had not been contacted for over 30 hours.

Chhang Dawa Sherpa, the team leader of the SST winter expedition team, said that the army's helicopter made "a search flight almost up to 7000m and returned back to Skardu".

"Unfortunately, they can't trace anything," he shared.

"The condition up in the mountain and even at the base camp is getting poor. We are looking for further progress, but the weather and winds are not permissible," he wrote.

In an update shared on Saturday night, Special Assistant to the Prime Minister on Overseas Pakistanis Zulfiqar Bukhari said Prime Minister Imran Khan and Chief of Army Staff Gen Qamar Javed Bajwa were "concerned and personally following all developments regarding our missing mountaineers".

"High altitude porters and Lama helis will restart search at the crack of dawn. Prayers needed from everyone for their safe return," he said on Twitter.

Earlier, it was reported that the three climbers had managed to summit K2, prompting congratulations from government officials, including the Gilgit-Baltistan governor and chief minister. However, no official statement has been released in this regard and it is currently unclear whether they managed to summit the peak on Friday or not.

Speaking to Dawn, an official from the expedition team said the only verified news was that the climbers had crossed the bottleneck which led many to assume that they had reached the summit.

Meanwhile, Sadpara's son, Sajid Sadpara, who was also part of the expedition, reached the K2 base camp after waiting for the three climbers at camp 3 for over 20 hours. Sajid was with the three up until the bottleneck, the most dangerous area of the mountain, and had returned to camp 3 after facing issues with his oxygen regulator.

According to Sajid, he was with the trio till 10am on Friday, when he had to turn back, adding that they were in good shape and going ahead with the ascent.

At midnight between Thursday and Friday, around the time they began their ascent to the peak from camp 3, Snorri's official Facebook page said the climbers were unable to rest over the day as "three other climbers needed shelter in their tent so there were a total of six people in the small tent".

"The climbing went well. They were feeling a little sick but are okay now," the post said.

However, more than seven hours later the team shared that there had been no news since camp 3.

"The GPS track is unclear going back and forth. I believe it is just some misreading from the [satellite] signal or low battery. We need to keep our faith and believe they will succeed."

The team later shared the update that the GPS had not updated Snorri's location in six hours.

"They have been climbing for 12.5 hours and [Snorri] mentioned 15 to 16 hours to the summit. Their chef at the base camp thinks they're in the bottleneck [...] His plan was to call me when he reached the summit. I am hoping for that plan to stick."

At 5pm on Friday, Snorri's team said they were in contact with the expedition team's chief and base camp manager.

"We have decided not to bother them and wait until they will contact [base camp manager]. We are not listening to other news, we are the only source to the team."

However, on Saturday the Snorri team said it had not heard from the three climbers. "The only news we have is that Sajid Ali [Sadpara's son] is descending safe from camp 3."

It also thanked the Pakistan Army for carrying out a search and rescue mission using a helicopter and the Icelandic ministry of foreign affairs for their cooperation.

The news of the missing mountaineers has prompted several hashtags to trend on Twitter, with netizens and politicians praying for their safe return.

President Arif Alvi said he hoped they were alive and fine. "These are very brave mountaineers. We pray for their safety," he said.

PPP Chairman Bilawal Bhutto-Zardari while praying for their safe return called for all possible efforts to be taken to locate the missing men.

Speaking about Sadpara, Bilawal said: "Finding him, a man who has risked his life to wave the national flag on the world's highest peaks, should be a priority."