Oil and Natural Gas Corp (ONGC) said it might take a year to fully rebuild the Bombay High North platform, which had produced a seventh of India's oil.

The company said it would try to restore part of the 100,000-barrel-a-day output in a few months.

The oil rig incident was only part of a disastrous week for western India where record monsoonal rains have downed power lines, collapsed walls, and caused floods and mudslides, leading to at least 785 deaths.

This extreme weather had pushed a nearby support vessel into Bombay High North, starting a fire that destroyed the platform, the support vessel and a nearby rig. The platform sank.

"We have picked up people from the sea and there were people who were in the water for more than 12 hours," Vice-Admiral of the Western Naval Command Madanjit Singh told a news conference.

At least 10 people have died and 367 had been rescued, according to the navy. Six divers remain trapped in the support vessel, and one or two people were still missing.

Torrential rain and high winds have been making rescue operations difficult. Coast Guard officials said helicopters, navy and coast guard ships, and civilian vessels were searching for any survivors of the fire.

ONGC said it would take a while to restore production. Building a new platform could take a year. In the meantime, sub-sea pipelines could be built to a nearby platform but this work could not start until the monsoonal rains ended in September.

Bombay High North was producing about 100,000 barrels a day. The field as a whole produced roughly 260,000 barrels a day, accounting for 38% per cent of all domestic oil production.

ONGC said other platforms in the field were still functioning normally and the fire was unlikely to have caused an oil spill as safety systems would automatically shut down production, and any leaking oil or gas would have been ignited by the flames.