Sri Lanka's government on Thursday expressed "regret" over the killing of civilians at a refugee centre in the island's east, but blamed the LTTE for using them as human shields.
"While we regret this whole episode, we want to say that national security is uppermost in our minds," Defence spokesman Keheliya Rambukwella told reporters here.
"The actions of the security forces was inevitable," he said.
Tamil Tiger rebels said 65 civilians were killed in the attack by government forces in the eastern district of Batticaloa on Wednesday.
Rambukwella said Tigers were attacking security forces and neighbouring villages with artillery and mortar bombs in the district and troops took counter action when the attacks intensified on Wednesday.
"The LTTE is using humans as shields to cover their operations," Media Minister Anura Yapa said adding "this is exactly what happened when they fired artillery and mortars from that end to the government side".
While the rebels and hospital sources said at least 65 people were killed in the attack, Nordic truce monitors said they counted 23 bodies at the scene on Wednesday.
Rambukwella said they were also told that 23 people were killed, but believed the casualties could rise.
"We urge your good selves to take immediate action regarding this matter and take steps to safeguard the internally displaced Tamil speaking people and other civilians," the legislators told the UN High Commissioner for Refugees.
The government also met with diplomats from the key donor nations to brief them on the situation, Rambukwella said.
The move came as the Amnesty International condemned the massacre of civilians and asked the government to order an immediate investigation.