Official sources said the Lankan Navymen attacked the fishermen with stones, nylon ropes and rods and took away their three boats.
Gnanasekaran, who suffered head injury, has been admitted to a hospital here while five others suffered minor injuries, they said, adding, the fishermen were near Katchatheevu, an islet ceded to Sri Lanka by India under an agreement in 1974.
The detained fishermen had been taken to Mannar district in Sri Lanka for being remanded there, the sources said.
On Sunday, the Lankan Navy allegedly took away at gun point the catch netted by fishermen who put to sea from here, when they were near Katchatheevu after surrounding 10 boats.
In another incident on the same day in Nagapattinam, eight fishermen of Vedaranyam village were injured in an attack allegedly by Sri Lankan naval personnel in mid-sea off Arukattuthurai in Tamil Nadu.
Today's attack comes a day after Tamil Nadu Chief Minister Jayalalithaa wrote to Prime Minister Manmohan Singh, charging the government with "soft handling" the issue of Sri Lankan Navy's alleged attacks on Tamil Nadu fishermen.
Jayalalithaa had said "soft handling" had emboldened the Sri Lankan Navy to attack and harass fishermen of Tamil Nadu with impunity, and asked the government to ensure that the island nation's navy refrains from doing so.
Ruling UPA key ally DMK chief M Karunanidhi had also slammed recurring attacks on Tamil Nadu fishermen and demanded that the Centre seek a strong and permanent solution to the vexed issue.
