An Indian couple falsified photographs of themselves at the top of Mount Everest to get their feat certified by Kathmandu, Nepal said Wednesday, after earlier saying the climb was valid.

Dinesh and Tarakeshwari Rathod, both police constables, said they reached the top of the world's highest mountain on May 23 -- but fellow climbers cast doubt on their claim, saying their photos at the summit were doctored.

Nepal's tourism department initially certified the couple's climb after speaking to their expedition organisers and government officials stationed at Everest base camp.

However, following the allegations, which gained speed online after climbers pointed out that the clothes they were wearing in different photos did not match, Kathmandu opened a probe.

‘The expedition agency has confirmed that the photos submitted to the department were morphed by the Indian couple in order to get the certificate,’ Nepal tourism official Gyanendra Kumar Shrestha told AFP.

‘The investigation is underway and the investigating committee is likely to unveil its report soon... and recommend punishment to those involved in the fraud,’ Shrestha told AFP.

It is not technically an offence to pretend to summit Everest.

However, Indian authorities have also opened a fraud case against the couple after eight other climbers filed a complaint against them, saying such a con belittled the efforts of genuine mountaineers.

Mohan Lamsal, owner of Makalu Adventures, which organised the couple's expedition, told AFP the pair had gone into hiding and failed to respond to the agency's request for the original digital copy of the photographs.

‘We... received photos from another Indian climber claiming that his photos were duplicated. While comparing those photos, we became sure that the photos submitted (by the couple) were fake,’ Lamsal said.

‘The two sherpas who assisted the expedition have (also) gone out of reach. We are trying to contact them.’

Nepal's investigation may pave the way for new rules on certifying summits, tourism official Shrestha said.

‘The government's liaison officer at base camp has to rely on the sherpas and expedition leader to certify claims,’ he said.

‘(We) need a serious review of the process of certifying climbers... the committee is likely to come up with some suggestions.’

Many successful Everest summiteers have gone on to make money or forge careers as motivational speakers and authors on the back of their feat.

A total of 456 people, including more than 250 foreigners, summited Everest during the recently concluded spring season after two consecutive years of deadly disasters that led to almost all attempts being abandoned.

Mountaineering is a major revenue-earner for the impoverished Himalayan nation and this year's string of successful summits is expected to boost the industry, which was left reeling after an earthquake last year killed almost 9,000 people nationwide.

Hundreds fled Everest last year after an earthquake-triggered avalanche at base camp killed 18 people.

Only one climber reached the top in 2014 after an avalanche killed 16 Nepali guides that year.