An increasing number of mountaineers at the Mount Everest base camp in Nepal are testing positive for Covid-19, raising fears of a serious outbreak, according to a BBC report on Wednesday.

Base camp officials said a number of mountaineers from Mount Everest with suspected Covid-19 symptoms had been flown to hospitals in Kathmandu for treatment and 17 of them had tested positive for the infection.

Staff at a private hospital in Kathmandu, the CIWEC clinic, confirmed to the BBC that patients had tested positive for coronavirus after arriving from Everest base camp.

"We have just received from Kathmandu confirmation of 17 positive cases in climbers flown out of Everest," said Lhakpa Nuru Sherpa, an official with the Himalayan Rescue Association which runs a medical clinic at the base camp.

The Nepalese government has so far denied having any knowledge of positive cases at Everest base camp, raising concerns that officials are downplaying the extent of the situation out of fear it will bring more pressure to close the mountain to expeditions.

Prem Subedi, the under-secretary at Nepal's Ministry of Culture, Tourism and Civil Aviation, told the BBC that the ministry was not aware of any coronavirus cases at base camp.

Nepal has issued a record 394 permits so far this year for expeditions to Mount Everest, the world's highest peak, despite the surging coronavirus pandemic. Everest had been closed to mountaineers last year because of the coronavirus pandemic but the season resumed this year as foreign expeditions climbers are a major source of revenue for the Nepalese government.

Authorities are mandating that visiting climbers quarantine in Nepal before proceeding to base camp, but concerns have been raised by some travel firms that there is a risk of a serious outbreak Covid-19. Many organisers had scrapped plans of taking expeditions to Mount Everest this year.