A Nepali climbing guide who went missing on Mount Everest for six days has been found crawling down to base camp in what has been described as a miraculous self-rescue.

Dawa Sherpa was assisting a Polish climber when he disappeared on 29 May above Camp 3, around 7,500m (24,600ft) above sea level. Hopes for his survival were slim as oxygen levels at that altitude are critically low.

He was thought to be another fatality, until he was spotted alive by a cleaning crew on Thursday.

"This is a true self-rescue,'" said Pemba Sherpa, executive director of 8K Expeditions which was overseeing search efforts. "Dawa managed to survive against all odds for days. It's nothing short of a miracle."

Five people have died so far in this year's climbing, three of them Nepalis who were involved in the Everest preparations, according to AFP News Agency.

More than 1,000 reached the Everest summit this season, making it the busiest on record.

An experienced climber, Dawa Sherpa is also known as Hillary Dawa Sherpa after famed mountaineer Edmund Hillary.

Dawa Sherpa was "slowly sliding through" the Khumbu Icefall toward Base Camp when he was found, Pemba Sherpa said, adding he was in overall good health.

"As far as I know, no one has survived alone at that altitude on Everest so far. This is a miracle to have survived for six days alone and descended safe. I think he must have lived inside the tents to keep himself safe," Pemba Sherpa said.

Before he was found, Dawa Sherpa's wife told AFP that she had offered last rite prayers for his sould.

On Wednesday, Chris Thrall, a climber and former British Royal Marine, posted a tribute on Instagram for the climbing guide, thinking he had died on the mountain.

In the video he recalled that Dawa Sherpa had "sat down for a rest with his backpack" as they descended from Camp 4, the highest campsite before the summit.

"And I turned and I said, 'Hillary, are you okay, brother?' He said, 'Yes, yes, fine Chris, please go, go!'" Thrall said. "This is nothing new, you know, I'd go ahead, he'd go ahead."

As Thrall went down he found a struggling Polish climber, and they continued descending together. But Dawa Sherpa never caught up with them.

In the days that followed, 8K Expeditions reportedly launched an aerial search but did not manage to find him.