Vaiko said following the end of the 45-day fishing ban period, Tamil Nadu fishermen who ventured out were "threatened" by the Sri Lankan navy who, he claimed, had stationed its ship in Katchatheevu.
"There is information that Chinese boats are also sighted there and Chinese personnel are on the Sri Lankan ship. This is an intimidation to India on our seas as well as international waters," an MDMK release quoting Vaiko said.
CPI state unit secretary D Pandian also urged Centre to act on this matter.
Katchatheevu, an islet in the Palk straits, was ceded to Sri Lanka by India in 1974 by way of a pact. Following continued attacks on Indian fishermen allegedly by the Lankan navy, Tamil Nadu Assembly had adopted resolutions twice seeking its retrieval.