An oil tanker with 37-member crew on board on Wednesday ran aground off the city coast under the impact of high velocity winds before the landfall of cyclone 'Nilam'. Coast Guard and other agencies have launched operations to rescue some crew members as a life boat carrying them capsized in choppy waters off Besant Nagar locality in South Chennai, 16 kms from here, Chennai Port Trust sources said.

'Pratibha Cauvery,' along with several ships berthed at the Chennai Port, was yesterday asked to go to the Outer Anchorage (OA) of the port as a precautionary measure before the severe cyclonic storm arrived, they said.

However, the ship, anchored about 3.56 nautical miles away from the Port yesterday, drifted and touched the shore near Elliots Beach.

"The ship was carrying 37 people on board," the sources said, adding that 15 of them tried to escape by life boat but were left stranded in the sea as the vessel capsized.

"So far four persons have been rescued. Coast Guard is coordinating with us", the sources said.

The 26,000 tonne capacity tanker had two tonnes of light diesel and furnace oil when the mishap occurred.