BY Mark Dummett BBC, Kinshasa

The United Nations and international aid agencies are sending their first mission to Uvira in eastern Democratic Republic of Congo, where fighting is feared to have displaced more than 50,000 people.

Clashes have taken place between the Rwandan army and a group of its former allies from the Congolese RCD rebel movement.

Civilians have been main victims of DR Congo's wars

Little aid has reached the area and fighting is reported to be worsening.

Residents and local aid organisations say that the fighting in the Hauts Plateaux region of South Kivu province has been getting much worse in recent weeks.

They fear that the effect on the local population has been catastrophic.

Truck-loads of Rwandan reinforcements have been crossing into DR Congo, while there are reports that helicopter gunships are being used to bomb villages.

Rebels fall out

Since the beginning of June, no aid has reached the displaced people, reported to number 50,000.

Most are feared to be sleeping in the open, in freezing temperatures, and at constant risk of being caught up in the fighting.

The UN and aid agencies are sending a mission to Uvira to evaluate their needs - but the escalation of the conflict and the mountainous terrain mean any information they find will be sketchy at best.

The fighting pits the Rwandan army and its RCD allies against a community known as the Banyamulenge - Congolese from the Tutsi ethnic group.

The Banyamulenge were the most loyal foot soldiers in the rebellion that toppled President Mobutu Sese Seko and brought the late Laurent Kabila to power.

They then joined the uprising launched by Rwanda and the RCD rebels four years ago to topple the Kabila government in Kinshasa.

At the beginning of the year a Banyamulenge commander, Patrick Masunzu, abandoned the rebellion, arguing that Rwanda was no longer protecting his community.

Since then Mr Masunzu is reported to have been joined by about 1,000 men and the conflict has become one of the most serious of the many small wars now taking place on Congolese soil.