CHENNAI, INDIA: Floods that have killed 210 people in Tamil Nadu began to recede on Thursday, giving rescue teams a chance to evacuate thousands of residents stranded by the heaviest cloudburst in the city of Chennai in over a century.

Floods and incessant rainfall cut off more than three million people from basic services and hampered rescue efforts by the army, which has so far evacuated 18,000 people from rooftops and outlying villages.

City authorities were deploying bulldozers and bags of concrete to repair collapsed roads, while several bridges were under water as urban lakes in the low-lying coastal city of six million overflowed.

Train services and flights to Chennai, capital of Tamil Nadu, remain cancelled and the navy has pressed fishing boats into service to evacuate people from the worst-hit suburbs to temples, schools and wedding halls.

A senior federal official said more than 700 people had been critically injured and were rushed to government hospitals by paramilitary forces.

Dhatwalia said the priority was to repair phone networks, distribute drinking water, medicines, food for infants and prevent the spread of water-borne diseases. Many firefighters from around Tamil Nadu have been pressed into service.

But new flooding problems continue to remain a concern with additional rainfall of 100-200 mm (4-8 inches) predicted from Thursday through Sunday.

In a 24-hour burst - the strongest in more than a century - 345 mm (14 inches) fell on parts of Chennai. As ground floor dwellings were flooded, residents sought shelter with upstairs neighbours.

Cultural activist V.R. Devika, 61, said many people were offering free accommodation and home cooking via social media.

"People are giving out food. Those with big vehicles are driving around rescuing people," she said by telephone.

Perumal, who drives a rented auto rickshaw, said the owners had taken the vehicle away and would return it only when the rain stopped. He said officials from different political parties had visited the area but done little to help.

"They write and they go, but they haven't come back or helped us," said Perumal, who gave only one name.