Accomplished climber Frank Ziebarth, seen in his Facebook profile photo, died on Mount Everest after reaching the summit without the use of bottled oxygen. (Facebook)

A mountain climber from Calgary has died on Mount Everest after making it to the summit without the use of bottled oxygen.

At least two climbing websites have confirmed the May 21 death of Frank Ziebarth, 29, who moved to the city two years ago from Germany.

Ziebarth is reported to have reached the summit on the Tibetan side, and was last seen at 8,700 metres determined to descend under his own strength.

"Very sadly, Frank could not make it back to high camp, suffering from hypothermia and obvious lack of oxygen," his climbing partners, Alexandre Pare, Manuel Pizarro and Anna Baranska said in a statement posted on EverestNews.com.

"It was later confirmed by fellow climbers that his body now rests peacefully at the bottom of the third step, high on Mount Everest."

His colleagues said Ziebarth was an accomplished high-altitude climber who had already made it to the top of at least three other peaks without the use of oxygen.

Pizarro declined an interview request. He said he will speak about what happened once he returns to Canada next week.

Word of Ziebarth's death shook his friends in Calgary, who left messages on the social networking site, Facebook. Ziebarth was engaged to Christina Ziegler of Calgary.

Attempting more difficult routes with fewer resources

There are unconfirmed reports that Ziebarth was the fifth person to die on the world's tallest peak this climbing season. About 300 people reached the top of the 8,849-metre high mountain this year — many of them in the last few weeks.

Veteran mountaineer Sharon Wood didn't know Ziebarth, but said climbing the iconic mountain is becoming so commonplace that some attempt more difficult routes with fewer resources — including trying to reach the summit without bottled oxygen to make the climb as pure an experience as possible.

'You've given it everything you had to get to the top but you have been too high, too long. That is the problem.'—Sharon Wood, mountaineer

"Climbing Everest without oxygen is related to style," she said from Canmore, Alta. "You are going for the maximum amount of efficiency. If you don't have a lot to back you up you have to be very proficient — that's good style."

Wood, the first North American woman to summit Everest, said some mountaineers want to separate themselves from less experienced climbers by making an already dangerous task even more challenging. But more challenge means more risk.

"There is a saying in the world of high-altitude alpinism that when you make it to the top, you are really only halfway there," said Wood, who was on bottled oxygen when she reached the summit of Mount Everest in 1986.

"The most difficult part of climbing an 8,000-metre peak is getting back down again. You've given it everything you had to get to the top but you have been too high, too long. That is the problem."