DEHRADUN – Thousands of Indian soldiers battled on Thursday to reach villages and towns cut off by flash floods and landslides in the country's north as officials warned at least 1,000 people may have been killed.

Helicopters and close to 10,000 soldiers have been deployed to reach tourists and pilgrims stranded after floods caused by torrential monsoon rains hit the Himalayan state of Uttarakhand at the weekend.

The soldiers were mobilizing to "provide leadership, succour, medical, air and engineer efforts", the army said in a statement.

Houses, buildings and vehicles have collapsed or been swept away by flooding rivers and landslides, while bridges and narrow roads have also been destroyed, leaving some 65,000 people stranded mainly at remote pilgrimage sites, officials said.

Torrential rains four and a half times as heavy as usual have hit Uttarakhand, known as the "Land of the Gods", where Hindu shrines and temples built high in the mountains attract many pilgrims.

One of those stranded was Indian cricket star Harbhajan Singh, who was attempting to reach a Sikh pilgrimage site but had to take refuge in a police station.

"Some people are saying that we're stuck but I wouldn't say that we're stuck, I'd say we've been saved by God," the spin bowler said. "With the kind of rainstorm we witnessed, anything could have happened. Many people lost their lives."

At least 138 people have been killed across Uttarakhand and two neighbouring states also hit by floods and landslides, officials said, but shrine authorities warned the toll was more than 1,000.

"We estimate more than 1,000 people have died as unattended bodies are scattered all around," said Ganesh Godiyal, chairman of a trust in charge of several shrines in the pilgrimage towns of Kedarnath and Badrinath.

Over the border in Nepal, floods and landslides also triggered by the monsoon have left at least 39 people dead mostly in remote parts of the country, officials said.

In India, the military operation was concentrating on reaching the worst-hit Kedarnath temple area, as families of those missing and stranded faced an anxious wait in Uttarakhand capital's Dehradun.

"Never seen anything like this... entire roads have vanished and villages destroyed... there's rubble everywhere," a military officer said, on condition of anonymity as he was not allowed to speak to the media.

One state lawmaker put the death toll at 2,000, although disaster management officials could not confirm the figure.

"The entire area is destroyed. Nothing is left," lawmaker Shaila Rani Rawat from Kedarnath told AFP.

Prime Minister Manmohan Singh said late on Wednesday the priority was rescuing those still stranded and helping the more than 10,000 people already evacuated, describing the floods as "most distressing".

Nearly 10,000 soldiers along with 13 teams from the National Disaster Response Force have been deployed for the rescue and relief effort, a statement from the prime minister said.

Local officials said 40 relief camps have been set up to house evacuated residents and tourists. Some 18 air force helicopters are ferrying many of those rescued to the camps.

Soldiers from the Indo-Tibetan Border Police have been building rope and log bridges across raging rivers to try to reach those stranded.

In New Delhi, the rain-swollen Yamuna river was swirling close to a level last recorded in 1978 when flash floods inundated parts of the Indian capital.

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 the country's lack of preparedness.