The heaviest rainfall in over a century caused widespread flooding across the southern Indian state of Tamil Nadu, driving thousands of people from their homes, shutting down factories and paralysing the airport in the state capital Chennai.

India's fourth-largest city is a major auto manufacturing and IT outsourcing hub for companies including Ford Motor, BMW AG, Infosys, Tata Consultancy Services and Cognizant Technology Solutions Corp.

Thousands of factories on the outskirts of the city were forced to close due to the deluge, which disrupted power supplies and swamped at least one runway at the international airport. About 25 flights were cancelled as of Wednesday morning, the national emergency operations centre said.

"We have started the rescue operation but the biggest challenge is to find a way to clear the inundated airport and main roads," said Anurag Gupta, a senior official at the National Disaster Management Authority in New Delhi.

Weather experts say the seasonal northeast monsoon was responsible for the flooding in the city of at least 6 million, which like many other parts of India lacks an adequate drainage system.

At least twice as much rain fell in the last 24 hours as the average for the whole month of December, private weather forecaster Skymet said, adding that the downpour would continue for another 24 hours.

Meteorologists had warned late last month that the remnants of Typhoon Marilyn, or In-Fa, and which had formed near the Philippines, could turn into a tropical depression and bring heavy rains to India's east coast.

RELIEF EFFORT

Prime Minister Narendra Modi has ordered rescue teams and paramilitary forces to launch an extensive relief and rescue operation in Chennai.

He had earlier blamed climate change for the rains in the southern state, speaking after returning from a global climate conference in Paris that has drawn attention to the vulnerability of tropical countries like India to extreme weather events.

Hundreds of divers and army rescue teams entered inundated homes, taking the injured to hospitals. Authorities said more than a million people were affected by the flooding, with some residents bemoaning the slow response of the relief teams.

Ramana Goda, 56, said his family was stuck in an area where 10 feet (3 m) of water covered some roads.

"The police want to help but there are no boats. We are trying not to panic," said Goda, who took refuge at a police station after fleeing his home with his family overnight.  - Reuters