Health officials working near the front line in Sri Lanka say heavy shelling in the newly-designated safety zone has killed hundreds of civilians in the past 24 hours.

One official has told the BBC the hospital where he is working had received the bodies of 378 people killed in just under 24 hours by artillery fire.

He said a further 1,122 people were being treated for injuries, and added that there were further bodies in other places, including by roads and on the beach.

Two health officials had earlier spoken of constant shelling of densely populated civilian areas.

They said the firing came from areas held by the Sri Lankan army but the Sri Lankan defence spokesman, Keheliya Rambukwella, said the accounts were propaganda from the Tamil tiger rebels.

The United Nations spokesman in Colombo, Gordon Weiss, says there has been no let up for civilians caught up in the conflict.

"Our assessment is that people stuck up there at the moment are in very very poor condition. They've had very little food delivered to them for months now," he said.

"We can see from the position of the people who are coming out of that area and winding up in camps that they're in a terrible condition. So we can only imagine that the people still stuck up there life has become... is even worse."

Meanwhile, the Liberation Tigers of Tamil Eelam (LTTE), claims up to 2,000 civilians may have been killed in the last 24 hours.

Mr Weiss says there have always been competing claims about casualty figures.

"The UN has said for some time now that thousands of civilians have been killed and wounded over the past few months," he said.

"We have no reason to believe that the toll on civilians has let up in any significant way since this last phase of the conflict."

The reported attack is the latest in a series of accusations and counter-accusations about who is harming civilians, tens of thousands of whom are trapped inside less than five square kilometres of battlefield.

The disparate accounts illustrate the difficulty of getting a clear picture from inside a war zone that is rarely opened to outsiders by either side, and where those present are not fully independent from pressure often delivered at gunpoint.

Both sides have repeatedly exaggerated battlefield accounts for propaganda purposes, and both deny accusations they are harming civilians.

Health officials said the places attacked were within what the Sri Lankan Government calls its 'new safety zone', a small area into which the army has asked civilians to move.

They said two hospitals were struggling to cope with the casualties and that people were hiding in bunkers and many makeshift tents had been burnt.

The officials say shells fell near medical facilities in very congested areas.

Sri Lanka's leaders believe their military offensive is close to defeating the Tamil rebels, who are holed up on the north-east coast, after 37 years of ethnic conflict.

At the height of their power in 2006, the Tigers - who want an independent Tamil homeland in the Sinhalese-majority island - controlled roughly a third of the island.

The Sri Lankan Government has refused all international calls for a ceasefire despite United Nations' reports last month saying up to 6,500 civilians may have been killed and 14,000 wounded in fighting since January.

It has also turned down requests to send humanitarian aid into the rebel territory, where the UN estimates about 50,000 civilians are trapped.

The Government says the number of civilians being held by the Tigers as a 'human shield' is less than 20,000.

Independent reporting from the conflict zone is impossible, as journalists are banned from travelling freely.

- BBC/AFP