Sri Lanka's Tamil Tiger rebels accused government forces of killing at least 45 people today in a fresh artillery and mortar attack.

sri lanka violent conflict 120509 06 The allegation came amid mounting international outrage over large-scale civilian deaths, with the European Union calling for Security Council action and the United States telling Sri Lanka to stop using heavy weapons.

A spokesman for the Liberation Tigers of Tamil Eelam (LTTE), whose fighters are battling to defend a tiny strip of coastal jungle, said a makeshift hospital packed with survivors of weekend attacks was hit by government forces.

"Heavy artillery and mortar attacks this morning hit the hospital and 45 people were killed there," LTTE spokesman S Puleedevan said by telephone. "Most of them were those injured in Sunday's attacks."

sri lanka violent conflict 120509 03 The LTTE says over 2,000 civilians were killed in Sri Lankan army attacks on Sunday, while the island's military has blamed any civilian deaths on the rebels - who it says are keeping people hostage to use them as human shields.

Sri Lanka's military also denies using heavy weapons in the area and insists it is moving slowly and carefully to avoid killing civilians.

The rival claims cannot be independently verified as independent journalists, diplomats and most aid agencies are barred from going anywhere near the conflict zone in the far northeast of the island.

Sri Lanka says the LTTE, which has been fighting for an independent Tamil homeland since the 1970s, now controls only four square kilometres of coastal jungle and are on the brink of total defeat.

But on Monday, UN Secretary-General Ban Ki-moon called for an immediate halt to the war.

sri lanka violent conflict 120509 05 "The secretary-general is appalled at the killing of hundreds of civilians in Sri Lanka over the weekend," his office said in a statement.

"Thousands of Sri Lankans have already died in the past several months due to the conflict, and more still remain in grave danger."

The UN spokesman in Colombo has described the weekend's events as a "bloodbath".

Unacceptably high level of civilian deaths

Top diplomats from Britain, France and Austria asked the UN Security Council to address the "appalling" crisis.

"The humanitarian situation in Sri Lanka is something the Security Council should address," British Foreign Secretary David Miliband said during a joint news conference with his counterparts from France, Bernard Kouchner, and Austria, Michael Spindelegger.

sri lanka violent conflict 120509 04 "There's no question that civilian life is being lost on a large scale," Miliband said, denouncing the "continued denial of visas and access" for the UN, NGOs and journalists.

The United States meanwhile said it was "deeply concerned".

"We think that there's an unacceptably high level of civilian casualties. We've repeatedly urged the Tamil Tigers to lay down its arms and allow the civilians to leave the safe zone," said State Department spokesman Ian Kelly.

He called on the government of Sri Lanka "to abide by its April 27th statement that combat operations have concluded, and that security forces should end the use of heavy weapons, which of course could cause civilian casualties".

Despite the outrage, the Sri Lanka issue is not on the agenda of the 15-member council as some powerful members, notably China and Russia, are opposed to taking action.

British Foreign Secretary David Miliband told reporters in ahead of Monday's meeting that the civilian situation in Sri Lanka merited the attention of the UN at all levels.