KINSHASA -- At least 48 people, most of them women and children who were hacked to death, have been killed in fighting in northeastern Congo involving rebels, tribal militias and the Ugandan army, UN officials said on Friday.

UN troops said they counted the bodies of 37 civilians killed during fighting on Thursday. Aid workers said fighting at the regional center of Bunia had intensified on Friday afternoon.

"All but three were women or children and there are very few signs of gunshot wounds. Most can be assumed to have been killed by machetes and other weapons," Colonel Tim Watts, chief of staff of the UN Force, told Reuters in Kinshasa.

Watts said many more were believed dead and a spokesman for the UN Force said 11 Ugandan soldiers were also thought to have been killed in the clashes, less than 50km (30 miles) from the vast state's border with Uganda.

The fighting pits rebels of the Congolese rally for Democracy-Liberation Movement (RCD-ML) and militias from the Lendu ethnic group against ethnic Hemas and the Ugandan Army, which at one time backed the RCD-ML.

Eastern Congo is scattered with rebel factions and militias, struggling for land and mineral resources with the help of foreign backers. The RCD-ML is a group that broke away from the main Rwandan-backed RCD, Congo's biggest rebel faction.

Thousands have been killed in fighting between Hema and Lendu in recent years in a conflict within a messy four-year civil war that has left an estimated two million people dead in the Democratic Republic of Congo.

Last week the presidents of Congo and Rwanda signed a peace agreement aimed at ending the devastating war, but the number of other factions involved has increased doubts over whether it will succeed. Congo's war erupted in 1998 when Rwanda and Uganda invaded to support rebels fighting the Kinshasa government. Zimbabwe, Angola and Namibia sent troops to back the Congolese Army in what has been dubbed "Africa's world war."

Last year the Ugandan Army said it had pulled out most of its troops from northeastern Congo, leaving a power vacuum which helped trigger tribal clashes and fighting between rebel groups.

But aid workers contacted by satellite telephone in Bunia on Friday said they had seen a Ugandan tank and soldiers heading towards the town center.