The Coast Guard, Coastal Marine Police and the local police have been asked to be vigilant round-the-clock as there was possibility of some terrorists involved in Sri Lanka's worst terror attack entering India through the sea route.
Police said Coast Guard personnel were patrolling the sea around Rameswaram in hover craft besides helicopter was also monitoring the situation.
Additional police personnel have been deployed on security duty at the Sri Ramanathaswamy Temple, thronged by pilgrims from across the country throughout the year, and devotees were thoroughly screened, they said.
Police presence had been increased at the railway station and bus stand also.
Thalaimannar in northern Sri Lanka is 18 nautical miles from Rameswaram and the travel time by a motorised boat is just under an hour.
Rameswaram was a hot bed of Sri Lankan Tamil refugee arrivals during the peak of ethnic strife in the neighbouring nation since the 1980s.
Seven suicide bombers believed to be members of an Islamist extremist group - the National Tawheed Jamath (NTJ) - carried out a series of devastating blasts that tore through three churches and luxury hotels in Sri Lanka on Easter Sunday, inflicting huge casualty.
No group has claimed responsibility for the attacks, but police have so far arrested 24 people - mostly members of the NIJ - in connection with the blasts.