But although Rasiah Ilanthirayan, a Tigers spokesman, confirmed a battle in the area, he denied that the base had been captured.
He said by telephone: "They [the special forces] have been trying to infiltrate our area and there was also a confrontation. But I deny that the camp has been captured."
Instead, he said Sri Lankan army shells hit a hospital complex in the island's northeast district of Trincomalee killing three civilians and wounding 11, according to Tamil Tiger soruces. But the military denied that it had fired.
The Tamil Tigers said that on Monday that shells had fallen in the town of Vakarai, about 240km northeast of Colombo.
Ilanthirayan said: "These people were sheltering in the hospital because they thought they would be safe under international law.
"The shells have hit the complex - one was a cluster bomb - and killed three people."
Neither aid organisations nor Nordic truce monitors have access to the Vakarai area, where there are thought to be 15,000 displaced ethnic Tamils, and casualty figures could not immediately be independantly verified.
Samarasinghe denied the claim.
He said: "We have not fired at the hospital premises in Vakarai today."
He said the special forces "only have multibarrel rockets and artillery. We don't have any cluster bombs".
Meanwhile, the UN has condemned the weekend's bomb attack on bus passengers which killed 21 people and left another 120 wounded, saying in a statement: "The United Nations calls for the protection of all civilians throughout the island."