Nearly 400 people were reportedly killed overnight Saturday by government shelling in what is supposed to be a "no-fire" zone of Sri Lanka.

The UN described the situation in Northern Sri Lanka as a "bloodbath" and stated that over 100 children had been killed over the weekend.

A photo supplied by a humanitarian group on Sunday shows civilians allegedly injured in government shelling, CNN reported.

Most of the roughly 378 dead are civilians, and another 1 200 were wounded, the aid workers said.

The government denies the assertion it shelled the "no-fire" zone, saying it is the Tamil Tiger rebels who have been killing civilians.

Tamil Tiger "attacks using heavy weapons in the no-fire zone have caused immense damage to the civilians entrapped in the area," the government information department said, quoting the military.

But the military did say it had advanced Saturday into areas previously held by the rebels, officially known as the Liberation Tigers of Tamil Eelam.

The pro-rebel Web site Tamilnet said rescue workers in the no-fire zone "have counted more than 1 200 bodies" and accused the army of "the use of cluster ammunition, multi-barrel rocket launchers and cannons.

About 165,000 displaced people are in the Vavuniya region, where the United Nations and other humanitarian groups are trying to get relief to them, an aid group said.

Meanwhile, a UK Channel 4 news team that had been detained by Sri Lankan authorities, after producing a report about the alleged abuse of Tamils, has left the country, news managers said Sunday.