The governments of Andhra Pradesh and Tamil Nadu have sounded high alert with the cyclonic storm `Thane' closing in on the east coast.
Meteorological forecasts said the cyclone is expected to lash the east cost between Nagapattinam and Chennai.
The cyclonic storm 'THANE' over southwest Bay of Bengal moved slightly westward and lay centered about 180 km east of Puducherry, 180 km southeast of Chennai and 400 km north-northeast of Trincomalee in Sri Lanka.
The storm is likely to move westwards and cross north Tamil Nadu coast between Nagapattinam and Chennai, close to Puducherry around early morning of 30 December, it said.
The two states have directed district collectors in vulnerable coastal districts to immediately evacuate people living in low-lying areas and closer to the shore.
The "very severe cyclonic storm", that lay centered over south-west Bay of Bengal this morning, is expected to move westwards and cross north Tamil Nadu coast between Nagapattinam and Chennai tomorrow morning.