Sri Lankan officials say military forces sank three Tamil Tiger rebel boats trying to attack the main port of Colombo.
They say naval craft blew up one boat after it entered a restricted zone around the port Saturday. The other two were destroyed as they tried to flee the scene.
There was no immediate casualty figure. But a Navy team detained three men found alive in the water. Officials say they believe the men were on one of the boats.
Sri Lankan officials say a foreign container vessel was slightly damaged during the incident.
Earlier this week, Tamil Tiger boats attacked a foreign merchant ship off the northern coast, sparking a fierce battle with the Sri Lankan navy.
The military says about 20 Tamil Tiger gunboats, including a suicide boat, were involved in the attack. The Sri Lankan navy called in air support and at least one Tamil vessel was sunk.
Fighting between Tamil rebels and government troops has escalated in recent months, despite a 2002 peace deal.
The rebels have been fighting since 1983 for an independent homeland in northern and eastern Sri Lanka. They say Tamils have been victimized for decades by the country's Sinhalese ethnic majority.
Some 67,000 people have died in the violence.
Some information for this report was provided by AFP and Reuters.