A Congolese army officer says at least 15 soldiers have been killed as two rival factions of the supposedly integrated armed forces clashed in eastern Congo over the last week. News of the clashes came as the United Nations sharply lowered the number of civilians believed to have been displaced by the fighting in the eastern part of the country.

After a week of sketchy reports of fighting coming out Walikale, a lawless mining town 120 km to the west of the eastern Congolese city of Goma, a local army officer has said that at least 15 of his men have been killed and 19 others injured.

Colonel Etienne Bintu, from the Rwandan backed former rebel group RCD-Goma, said that his men had been killed when their units were attacked by the pro-Kinshasa Mai Mai militia that is now supposed be an ally in the newly integrated Congolese army.

Colonel Bintu says he has no idea how many Mai Mai may have been killed or injured but he says a "precarious calm" has returned to the town, so he might be able to gather more information soon.

The clashes highlight the problems that need to be overcome before Congo's army can be fully integrated.

A five-year war that sucked in six neighboring countries and killed three million people is officially over, but the former foes still don't trust each other and the transition from conflict to elections has been rocked by several crises.

One such crisis was a rebellion in eastern Congo by a dissident army officer. Government forces this week re-took a lakeside base rebel General Laurent Nkunda has held for four months, but local authorities had said thousands of civilians had fled as a result.

U.N. humanitarian workers in North Kivu, the Congolese province where many of the displaced fled, said Friday that a initial assessment indicates roughly 20,000 civilians were on the move.

The aid workers stressed that these were initial assessments made in four areas, but the figure is far lower than the 100,000 initially suggested by the local authorities.

The North Kivu governor, also a member RCD-Goma, said that the civilians were predominantly Congolese of Rwandan origin and they had fled fearing reprisals by government soldiers accusing them of sheltering rebels.

There have been no immediate reports of reprisals. However, a diplomat in Kigali said that Rwandan authorities have already "expressed concern of ethnic cleansing of Congolese of Rwandan descent."

Eastern Congo has for a long time been a flashpoint in the vast African country. Rwanda has invaded twice in the last decade, saying it had a right to do so to hunt down Hutu extremists that took part in the 1994 genocide.

And following several crises in Congo, Kigali has threatened to intervene militarily a number of times this year as Congo's peace process moves towards elections, due in less than a year's time.