India on Wednesday deployed troops to Tamil Nadu and closed the main airport after heavy rains exacerbated weeks of flooding that have killed nearly 200 people in the southern coastal state.

Thousands of passengers were left stranded at the international airport in the state capital Chennai after flooding on the runway forced the cancellation of dozens of flights.

Authorities said thousands of rescuers carrying diving equipment, inflatable boats and medical equipment were also battling to evacuate victims across the flooded state.

"At least 10,000 police personnel and trained swimmers are being deployed to help with the rescue effort," said Chennai police chief JK Tripathy.

He said 186 people had been reported killed in the floods, now in their fourth week.

"The situation is a little grim. Some urban areas are totally flooded," said S.P Selvan, deputy inspector general of the National Disaster Response Force.

"If the rains hold off, the situation will improve, but if they start up again tonight there will be more trouble," he told AFP.

Authorities said the airport would remain shut until at least Thursday, hampering efforts to get relief supplies in.

The head of the Indian Meteorological Department, LS Rathore, said the heavy rain was expected to continue "for at least the next 72 hours".

"The water bodies in this region have become saturated and don't have the capacity to take in any more water," he added.

India's Prime Minister Narendra Modi cited the floods as a consequence of climate change in his weekly radio address on Sunday, a day before meeting with world leaders at a global climate summit in Paris.

Modi has repeatedly called on developed countries to do more to combat the impact of global warming on the world's poor, who experts say will be disproportionately affected.

India suffers severe flooding every year during the annual monsoon rains from June to September.

Hundreds died in the northern city of Srinagar in September 2014 when the rain-swollen River Jhelum burst its banks, leaving thousands stranded on rooftops.

Parts of Chennai were without power on Wednesday and television footage showed flood-hit residents wading through waist-deep water, many carrying their belongings on their heads or in small boats.

Bus and rail services were also hit, with many commuter trains into Chennai cancelled. Television footage from the state showed railway bridges in some areas had been washed away.

Local media said schools in the capital had been closed and exams postponed because of the floods.