The incident happened about 90 nautical miles north east of Chennai, navy sources said. Meanwhile, an official release said a fire broke out on board the 15.6 metre-long interceptor craft while it was on routine deployment at about 2 AM.
"The fire caused extensive damage to the Fibre-glass Reinforced Plastic (FRP) hull of the craft resulting in sinking of the boat despite all out efforts by the crew to save it. There were no casualties," it said.
An inquiry has been ordered to investigate the incident, it said. Navy officials did not provide further details, including the number of crew on board the craft.