Sri Lankan Navy early on Saturday fired at three suspected Tamil Tiger boats spotted in the seas off the capital Colombo.
Defense officials said that three suspicious boats were spotted close to the capital around 5:30 a.m. local time (0000 GMT).
The Navy fired at the boats destroying one of them while two other boats had fled the scene.
The Navy said a search operation had been launched in the entire coastal line.
The officials were blaming the Liberation Tigers of Tamil Eelam (LTTE) rebels for the attempted attack on the Navy's coastal guard.