The death toll from flooding and landslides following heavy monsoon rains in the northern Indian state of Uttarakhand has passed 500.
Searchers have recovered scores of bodies from the Ganges river, and tens of thousands are still stranded or missing.
Raging rivers have swept away houses, buildings and entire villages.
A large proportion of those stranded are Hindu pilgrims visiting local shrines with many reported trapped around the holy town of Kedarnath, located in a valley in the mountainous region.
State Chief Minister Vijay Bahuguna has described the floods as a "Himalayan tsunami".
Officials say that the number of dead could exceed 1000 people, although the exact number will be known only after a survey of the entire region is completed, the BBC reports.
Flood-related deaths have also been reported in Himachal Pradesh and Uttar Pradesh states and neighbouring Nepal.
The monsoon season generally lasts from June to September but this year the rain in the north of India and parts of Nepal has been heavier than usual.
Media reports say military helicopters and the army are mainly targeting Kedarnath, where portions of a famous Hindu temple have been washed away and the shrine is "submerged in mud and slush".
Many visiting pilgrims and tourists in Kedarnath, in Rudraprayag district, remain unaccounted for, officials say.
Local police chief Ajay Chadha told the BBC that while no-one was stranded in the town itself, thousands remain marooned in the hills that surround it.
He said they were being brought down to Kedarnath and would be evacuated on Friday morning.
Mr Chadha said in one area troops had made a rope-bridge, which had been used to rescue at least 1,200 people.