"Following the receipt of the intelligence inputs that there was a possibility of attack through the sea route, three Offshore Patrolling Vessels have been patrolling the western coast," Coast Guard sources said.
The offshore patrol vessels, the biggest ships with the Coast Guard, are out at sea despite the monsoons when waters are very rough and most small boats do not sail due to bad conditions, they said.
All crew, including ships and hovercraft's, stationed at other ports on the western coast have been told to be prepared to sail at short notice, the sources said.
Inspector General Coast Guard (Region West) Rajendra Singh refused to comment on the deployment of vessels and other measures being taken.
"All measures are being taken to ensure that no incursions are made into the country illegally through the sea route," Singh said.
Union Home Minister P C Chidambaram had said on June 30 that intelligence inputs have indicated of a possible threat to the states of Maharashtra, Goa and Gujarat from the sea.
Security along the western coast has been tightened following the November 26 terror strikes when ten armed gunmen entered Mumbai through the sea route using a hijacked Indian fishing vessel.
Over 160 persons were killed and 200 injured in the terror strike.
The Navy and the Coast Guard have conducted multiple exercises off the coast following the terror strikes to ensure security of the coasts.