About 4000 Indian fishermen set out to sea at the end of a 48-day ban, imposed to enable fish breeding.
Assistant Director of Fisheries in Ramanthapuram district Gobinath said officials have warned the fishermen against crossing the Sri lankan maritime boundary line.
He said severe action would be taken against those who had left town without obtaining the required permission
Gopinath said the Lankan Navy has deployed naval boats along IMBL to prevent the fishermen from crossing over into their territorial waters.
The Indian Coast Guard had also deployed sufficient force in the area to advice fishermen not to cross the IMBL.