Mumbai - Three people died and two were missing at sea as annual monsoon rains Tuesday caused floods in India's south that saw parts of Kerala state flooded and fishing in the Arabian Sea curtailed, reports said.

Two women were killed after a coconut trees uprooted by the heavy rains fell on them and a man was killed when a tree landed on a passenger bus in Kerala, Press Trust of India reported.

Elsewhere in the state, hundreds of families were moved to relief camps as villages in low-lying districts were flooded after the monsoon hit Friday, a week earlier than expected PTI said.

The heavy rains and rough winds also saw several boats capsize off India's western coast, leading a local weather department to warn fishermen not to go to sea.

"Gusty winds and heavy rains will continue for the next 24 hours and we have sent a warning to fishermen asking them not to venture out to sea," weather official K.V. Singh said from the western coastal state of Goa where five trawlers capsized Tuesday. One sailor was reported missing.

Early Tuesday morning, a merchant vessel with 21 people aboard ran aground because of the strong winds and current, the Indian Coast Guard said.

"Twenty were rescued and handed over to port authorities," Commandant M. Prasad told AFP, adding that one person remained missing.

The advance of the rains upwards from the south is keenly watched as two-thirds of the country's billion-plus population earn their livelihood from agriculture, but poor infrastructure often means heavy flooding and loss of life.

Last year 400 people died in the financial hub Mumbai, in western Maharashtra state, after nearly 100 centimetres (40 inches) of rain fell in 24 hours.

The state's top official however promised that there would be no repeat of that disaster.

A project to desilt the river that runs through the city, to prevent this year's rains from overrunning badly neglected drainage facilities, has almost been completed, he said.

"I assure Mumbai's citizens that there won't be a repeat of last year during the monsoons," Chief Minister Vilasrao Deshmukh was quoted as saying by the Hindustan Times Tuesday.