DEHRADUN: India's military 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 rescue tourists and pilgrims stranded after floods caused by torrential monsoon rains hit the Himalayan state of Uttarakhand at the weekend.

Some 1,400 people have been evacuated in the past 24 hours as the military takes advantage of clearer weather, but another 18,000 are still stranded, the air force said.

"Our priority is to take out the children and women first by helicopter," said Ajay Chadha, chief of the Indo-Tibetan Border Police.

"We hope to rescue all the living and then start the scavenging task," Chadha said in New Delhi, referring to the task of finding the dead.

Houses, buildings and vehicles have collapsed or been swept away by overflowing rivers and landslides, while bridges and narrow roads leading to pilgrimage towns have also been destroyed, 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.

"There are some 3,000 of us stuck in Gangotri (a pilgrimage site) for the past few days and there is no food, no drinking water or assurances from the government," a pilgrim, Parwinder Singh, told CNN-IBN by telephone.

"It is very difficult to move from here," he added.

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.

Indian paramilitary officers have been building rope and log bridges across raging rivers to try to reach those stranded. Television footage showed pilgrims using ropes and makeshift ladders to climb down cliffs to reach safer ground.

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 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," said the spin bowler, who was later flown out of the flood-hit area by military chopper.

"With the kind of rainstorm we witnessed, anything could have happened. Many people lost their lives," the cricketer said.

Figures for the death toll have varied considerably, underscoring the difficulty of reaching isolated areas.

An Uttarakhand state lawmaker, Shaila Rani Rawat, put the death toll at 2,000, but disaster management officials could not confirm this.

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

Relief camps have been set up to house evacuated residents and tourists. Some 30 aircraft are ferrying many of those rescued to the camps, while 14 tonnes of food and relief aid has been dropped in remote areas, the air force said.

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.