Indian priests are planning to cremate hundreds of flood victims as heavy rains halted the search for thousands stranded in the devastated Himalayan region, officials said.

Up to 1,000 people are feared dead and more than 8,000 mainly pilgrims and tourists are still awaiting rescue, nine days after flash floods and landslides caused by torrential monsoon rains hit the northern state of Uttarakhand.

"Five-hundred-and-eighty people have lost their lives and many more bodies are yet to be pulled out from isolated areas that are completely cut-off," K N Pandey, an official with the state disaster management team, told the AFP news agency on Monday.

Preparations were under way for a mass cremation in the flood-ravaged holy town of Kedarnath, with rescue workers ordered to collect tonnes of fire wood, amid concerns of an outbreak of disease from rotting bodies, officials said.

"We have decided to start [a] mass cremation today. The priests of temples have been requested to participate in the final rites," Pandey said.

Military helicopters have been grounded because of bad weather, suspending the evacuation by air of those still stranded, many without food and water, in remote areas of the state, known as the "Land of the Gods" for its revered Hindu shrines.

"We can only use the helicopters when the weather is clear. Rescue work can only resume when rains stop," said a senior army official in New Delhi.

Raging rivers

Helicopters and thousands of soldiers have been deployed to help with the rescue efforts, with thousands of people already evacuated since the rains hit on June 15.

Soldiers along with the Indo-Tibetan Border Police have been using harnesses and erecting rope bridges across flooded rivers as part of efforts to move people to safety.

Raging rivers have swept away houses, buildings and even entire villages in the state, which was packed with travellers in what is a peak tourist season.

More than 1,000 bridges have been damaged along with roads, cutting off hard-hit villages and towns.

In the adjacent state of Himachal Pradesh, 20 people have also been killed.

Floods and landslides from monsoon rains have also struck neighbouring Nepal, leaving at least 39 people dead, according to the government in Kathmandu.

The monsoon, which covers the subcontinent from June to September, usually brings some flooding. But the heavy rains arrived early this year, catching many by surprise and exposing a lack of preparedness.