Security has been stepped up in this island following an alert from the Intelligence Bureau that terrorists plan to sneak in through the Palk Strait from Jaffna in Sri Lanka and attack Madurai and Mayiladuthurai in the state, police said.
Superintendent of Police Mayilvahanan said there was information that eight terrorists plan to infiltrate by sea and coastal people have been advised to inform police in case they saw any strangers.
Patrolling of coastal areas has been intensified since last night, he said.
Officials said the IB alert has been conveyed to all units of the Intelligence wing, Coast Guard and Naval personnel.
The SP said 300 boats, which returned after fishing in the Palk Strait this morning, were checked thoroughly.
Coast Guard officials said two hover crafts, two small ships and a big ship from Chennai have been deployed in the Palk Strait to monitor the sea to prevent infiltration.
An Indian naval helicopter has also been engaged. Police said they had given a telephone number, 1093, to all hamlets in the coastal areas to enable people inform police in case any stranger comes in the guise of fishermen.
The SP said vigil has been intensified from Mandapam to Rameswaram, and security for Rameswaram temple where people from north India come in large numbers, tightened.
Meanwhile, Nagapattinam Fisheries department officials said the state fishermen have been warned not to cross the International Maritime Boundary Line.