The Indian authorities have launched a rescue operation for a 37-year-old mountaineer, a one-time resident of Singapore, who went missing during a climb on Mount Trishul, a Himalayan peak.

Dr Peter Wittek, a research scientist who did his PhD in computer science at the National University of Singapore, was part of a team of six who were climbing the 7,120m-high Mount Trishul 1.

Officials in India told The Straits Times five members of the team, including three Singaporeans, are safe and a rescue operation for Dr Wittek, identified as a Hungarian national, has been launched.

Ms Swati Bhadoriya, district magistrate of Chamoli, identified the three Singaporeans as Kong Xieheng, Nicholas Chee and Ong Siong Hwai.

"While they were coming down (from Mount Tris-hul), they were hit by an avalanche. They (five members of the team) themselves came down to the base camp," Mr Sanjay Gunjiyal, inspector-general of police at the Uttarakhand State Disaster Response Force, told ST.

"This is considered one of the toughest peaks in the world. It requires a lot of expertise. This particular patch is highly avalanche-prone," he added.

A rescue team of six is on its way, he said, but it could take at least three days to reach the spot where Dr Wittek was last seen.

The authorities are also gearing up to launch a helicopter rescue, which has been delayed due to low visibility. The helicopter could take off tomorrow, Mr Gunjiyal said.

The expedition has been described as the first Singapore attempt on Mount Trishul, on a website (www.biodune.com) run by Mr Teshil Gangaram, a Singapore resident, who was part of the team of six.

On the website, Mr Gangaram noted: "To go light, we used a variety of dry food. In Singapore, we managed to get hold of dry mushroom, shrimps, fish, dried meat, mangoes, guavas and prunes... As we finished packing for our 11 days of meals, the weight amounted to 10kg per person."

All team members are avid mountaineers.

One website says Mr Kong, 32, is the first Singaporean to climb Khan Tengri on the China-Kyrgyzstan-Kazakhstan border. Mr Chee, 30, is the first Singaporean to climb Lenin Peak (7,134m) in Kyrgyzstan, while Mr Ong, 29, has scaled peaks in Malaysia.

Dr Wittek is an assistant professor at the University of Toronto, working on quantum-enhanced machine learning.