Two years ago he got within 600 metres of the summit of K2 before being forced to turn back, ending his attempt to become the first Irishman to climb the world’s most dangerous mountain.

This year, after another bout of intensive training at his home in Alaska, Gerard McDonnell made the return journey to the Himalayas in Pakistan, determined to give it another go. On Friday, at 3pm Irish time, the Irishman achieved his lifetime ambition when he stood on the peak of the so-called “savage mountain”, 8,611m above ground level.

As friends back home reacted excitedly to the news of McDonnell’s success the reality was that his mission was only at the halfway stage. A tricky descent, made all the more dangerous by the exhaustion experienced at high altitude, had still to be navigated.

Yesterday there were fears that McDonnell’s triumph may have turned to disaster as news began to circulate that at least 12 climbers making their descent from the summit had run into difficulties. McDonnell was reported to be among those missing.

Reports late last night suggested that a lone figure had been seen making their way down the mountain. Friends and family of McDonnell hoped it was Gerard. Last night JJ, his older brother, was making his way home from Lanzarote, the Canaries, where he was on holiday, to be with his mother in Limerick where they awaited further news.

Mountaineers fear that this K2 mission could prove to be one of the worst on record. In Everest in 1996, eight people died in one day in poor weather in what is considered to be the worst mountaineering tragedy in the history of the sport.

It is understood problems arose at an area of the mountain known as the Bottleneck after the fixed ropes were torn away. This section of the climb is about 8,000m above sea level and getting stuck there would put mountaineers at extreme risk.

A group of six or seven climbers, including one who fell and broke either a leg or an arm, were effectively trapped and forced to negotiate a descent without the support that ropes would have given them. Unofficial reports last night suggested some of these climbers were descending while others were stuck above the Bottleneck.

Pat Falvey, a friend of McDonnell and one of Ireland’s best-known mountaineers, said: “The situation on the mountain is very serious and the reports we are getting, so far, are not good. People are missing, people are stuck at high altitudes and it would seem that some climbers are gone.

“It is difficult to get information because rescue attempts are ongoing, but of the 17 who were coming down, we know that six are trapped and six are reported missing”.

Falvey said Cecilie Skog, the wife of Rolf Bae, a Norwegian who was also descending, witnessed her husband and “possibly three others being swept away”.

“She is on her way down, but the news is devastating. Bae and Gerard would be good friends and there is a chance they were descending together. We just don’t know,” he said.

Falvey was hopeful that rescue attempts could reach some of the climbers but was concerned that many would be exhausted after 48 hours of continuous climbing, during which they reached the summit and then turned around immediately to begin making their descent.

Falvey also said that while it was possible to negotiate difficult parts of the mountain without fixed ropes, this would be more dangerous, especially given how tired the climbers would be.

“Time is really important here. You can’t stay at high altitude. All these climbers would be exhausted and it is vital that they get help. High-altitude porters are making their way to them and the hope is they will get there. The weather is good and is expected to stay that way for a while,” he said.

Falvey has described McDonnell as one of the best all-round Irish climbers. “He is a very driven, very motivated, guy. He has lived in Alaska for 10 years where he has honed his climbing and survival skills”.

McDonnell reached the top at about 3pm Irish time on Friday after spending eight weeks on the mountain, on the border between Pakistan and China.

Friends yesterday posted messages of support on the Norit team website as concerns grew for his safety.

“Please God, let Ger be one of the climbers descending from the Bottleneck. Our hearts are filled with fear but our thoughts are positive. Come home safe to us,” one said.

Another message from Terence “Banjo” Bannon, an Irish climber from Newry who has attempted K2 in the past, said: “Ger and all the climbers. Thoughts and Prayers are with you as you descend. May you find the safety of camp soon and come home to celebrate your success”.

Bannon was with McDonnell in 2006 when the Limerick man’s previous bid to climb K2 ended after he was hit by a rock fall and was airlifted to hospital. Bannon stayed on and teamed up with Russian climbers, but four of the team were killed in an avalanche close to the summit. It was Bannon’s third attempt on the mountain and he vowed he would never go back.

McDonnell is one of a group that includes Dutch, Australian and Nepalese climbers.

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