French troops leading an international force engaged in a firefight with gunmen Saturday for the first time in their mission to stabilize this northeastern Congolese town ravaged by tribal fighting.

The special forces returned small arms and light tank fire after they were fired on by gunmen as the French patrolled near Dele (search), a village about 4 miles south of Bunia, said spokesman Col. Gerard Dubois.

The shooting lasted about 20 minutes; there were no French casualties, he said. It was not clear whether the assailants suffered any casualties.

The French patrol of about 70 troops and 20 vehicles, including one light tank fitted with a 90-mm gun, stopped when the firing started, and the soldiers took up positions in the long grass on the side of the muddy road.

Bunia is the capital of resource-rich Ituri province, which has been the scene of some of the worst atrocities of Congo's 5-year-old civil war.

The troops are part of a French-led international force that began deploying to Bunia on June 6 in an attempt to stem fighting between Lendu (search) and Hema (search) tribal factions that has killed hundreds of people in and around the town.

The Hema faction, known as the Union of Congolese Patriots (search), which controls Bunia, said it was Lendu fighters who fired on the French on Saturday.

A few dozen Hema fighters passed the French troops when the firing started. Some cheered as the French opened fire.

"We were advancing on our traditional enemy (the Lendu), and the French troops came from behind us and told us to stop and that they would move ahead of us," UPC security chief Saba Rafiki told The Associated Press. "The Lendu attempted to fight the French but fled after a short while when the French began using heavy weapons."

It was not possible to contact Lendu militia who are in the rolling green hills that surround Bunia.

There are about 400 French troops in Bunia. At full strength the force will have 1,400 troops, some 800 of whom will be deployed in Bunia. The remainder will be stationed at the force's logistics base in Entebbe in neighboring Uganda. Ten French Mirage jets connected to the force are based in N'djamena, Chad and Libreville, Gabon.

The force, which is to deploy for three months, is supposed to reinforce some 750 U.N. troops in Bunia who can only fire in self-defense and have not attempted to stem the violence.

The international force is authorized to shoot to kill if necessary, but it does not have the mandate to disarm the fighters or demilitarize the town.

Despite the deployment of the French forces, the town remains unstable and reports of looting, abductions and killings continue to surface.

Manodje Mounoubai, spokesman for the U.N. mission in Congo, said U.N. officials had heard reports that there were "more than one" mass graves in Bunia. But UPC fighters deployed in the area of the suspected graves have prevented U.N. personnel from investigating them.

The French-led force does not want to engage the UPC until it has increased its strength, Mounoubai said.

Congo's civil war erupted in August 1998 when neighboring Rwanda and Uganda sent troops into Congo to support rebels seeking to oust then-Congolese President Laurent Kabila. They accused him of supporting insurgents from their countries whom they said were threatening regional security.

Zimbabwe, Angola and Namibia sent troops to back government forces.

The foreign troops have withdrawn, but fighting between rival rebel and tribal factions continues in eastern and northern Congo.