Meanwhile, a pro-rebel website said troops were amassing heavy weapons along the de facto border in the island's north and there were long range attacks.
The fighting started after Naval personnel intercepted a group of Sea Tiger boats moving toward the Pulmodai area on the northeast coast.
The LTTE said at least 26 civilians were killed in attacks carried out by the military on Monday, but did not say if they suffered any losses.
As the island heads for elections, two major factors worry Sri Lankan President Mahinda Rajapaksa. One is the division in the Sinhala vote and the other is the prospect of the Tamils and Muslims voting heavily against him.
Unlike in the presidential polls, victory might not have been complete, at least as yet, for Mahinda Rajapaksa's electoral rivals. While his one-time aide and confidant, Maithripala Sirisena, became president without any issues after defeating him, incumbent Prime Minister Ranil Wickremesinghe, who again may not command an absolute majority in the 225-member parliament, would have to count on his 'national government' concept to carry the day and the nation with him, this time round, says N Sathiya Moorthy.