The India Meteorological Department said Cyclone Gaja had intensified into a severe cyclonic storm and is expected to make landfall in Tamil Nadu by Friday morning. The weather department had earlier predicted that Gaja would make landfall by Thursday night, but in its update at 10.30 pm, said the storm had made slow progress in the last six hours, leading to a delay.

Wind speeds of 100 km per hour to 110 km per hour are expected on Thursday night, before the severe cyclonic storm weakens to a cyclonic storm by early on Friday and to a deep depression by noon, the IMD update said. The storm was centred over southwest Bay of Bengal at 8.30 pm on Thursday, and is likely to move west-southwestwards.

The department forecast heavy rainfall in parts of Tamil Nadu and Puducherry and extremely heavy rainfall in isolated places in Cuddalore, Nagappattinam, Karaikal, Tiruvarur, Thanjavur, Pudukkottai, Tuticorin and Ramanathapuram districts.

The Tamil Nadu government said 1,313 people have been relocated to relief camps in Nagapattinam and an evacuation operation is under way to take people in low-lying areas to higher ground before the storm, PTI reported.

The government has announced helpline numbers - 1070 (state-level) and 1077 (districts) - for those who may need assistance during the storm.

Tamil Nadu Revenue and Disaster Management Minister RB Udayakumar asked people living in huts and low-lying areas in Nagappattinam to move to safer ground. “Stay calm and don’t panic. Rely on official information from from India Meteorological Department, state disaster management authority’s Facebook page and Twitter handles,” the minister told The Times of India.

Meanwhile, the Southern Railways announced the cancellation of four trains, including three from Chennai to Nagapattinam, Tiruvarur and Thanjavur districts, and the diversion of four express trains.

The state government has kept 30,500 rescue personnel on standby, while district collectors of Thanjavur, Tiruvarur, Pudukottai, Nagapattinam, Cuddalore and Ramanathapuram have asked schools and colleges not to open. The government has deployed around 15 disaster response teams. Schools in Puducherry and Cuddalore district in Tamil Nadu have declared Friday a holiday.

Fishermen have been advised not to venture into the sea off Tamil Nadu and Puducherry and adjoining south Andhra Pradesh coasts for the next 24 hours.