The United Nations appealed to church leaders in northeastern Congo (search) on Saturday to help find two missing agency military observers, after a cease-fire aimed at ending several days of vicious tribal fighting in the area took hold.

There have been reports that the unarmed observers — one Jordanian, the other Nigerian — were killed in the fighting between the rival Lendu and Hema tribes, said Col. Daniel Vollot, commander of the U.N. forces in the region.

"But I don't want to believe that," he said.

The clashes, which have killed at least 100 people, began last week after Uganda withdrew 6,000 troops from Congo's resource-rich Ituri region and its capital, Bunia. The cease-fire was signed Friday and the United Nations is trying to assemble a peacekeeping force to augment more than 750 U.N. soldiers from Uruguay already there.

Efforts to find the two U.N. observers were delayed because it was unclear which tribal faction controlled the town of Mongbwalu, a gold mining center near Bunia where the two men were last seen Tuesday.

"Today we are trying to get in touch with church leaders to use their extensive information network to find out what happened to the officers," Vollot said.

There were no major clashes in and around Bunia overnight between the Hema (search), who control the town, and the Lendu (search), who have taken up positions in the surrounding hills. Only sporadic gunfire could be heard outside town.

The cease-fire commits the two sides to demilitarizing Bunia and confining their fighters to temporary quarters.

Tens of thousands of people have fled Bunia since the latest fighting began. Hemas and Lendus have sparred for centuries over land and other resources in Ituri, but the clashes became deadlier when civil war broke out in Congo in 1998 and modern weapons flowed into the region.

The U.N. Security Council has demanded an end to the killings in Congo. Secretary-General Kofi Annan has asked France to lead the force and provide up to 1,000 troops. But the French say they will not accept unless other nations join the force.

Council diplomats said Annan has asked about 20 countries for troops and some indicated they were prepared to contribute, including South Africa and Angola.

Vollot said French military officers and others were expected to arrive in Congo over the weekend to prepare for a peacekeeping deployment.

Congo's civil war broke out when Uganda (search) and Rwanda (search) sent troops to back rebels seeking to oust then-President Laurent Kabila. The Ugandan and Congolese governments then began using Lendu and Hema tribesmen as proxy fighters to battle over Ituri's resources.

Most foreign troops from the six countries that backed the rebels and the government have withdrawn after a series of peace agreements.