Sri Lanka's Navy took 13 Indian fishermen into custody on Sunday for allegedly fishing in the country's territorial waters.
The fishermen hailed from Ramanathapuram district of southern Tamil Nadu state. Two trawlers were also seized.
"We have been continuously opposing the unilateral attack on Indian fishermen but in spite of all this, these types of incidents continue to happen," said C.R. Senthilvel, general secretary of the Tamil Nadu fishermen's association.
It was the second such incident of the month. On December 11, 27 Indian fishermen were arrested and their five trawlers seized.
India shares an expansive oceanic border with Sri Lanka without any perceptible demarcation and fishermen on both sides ignore rules while netting their catch.
Sri Lanka has long fumed over poaching and illegal fishing by Indian fishermen that it says depletes the catch of its own fishermen.
Fishermen from both countries frequently stray into each other's territory and end up spending years in jails.