Insurgents ambushed a U.N. convoy in eastern Congo on Sunday, killing two South African peacekeepers and wounding nine others in a bloody attack that further threatened the shaky peace in the vast Central African county.

The two U.N. trucks were attacked in Rugari, 25 miles north of Goma, the main city in eastern Congo, said Jacqueline Chenard, the U.N. spokeswoman in Goma. Residents said the insurgents were Rwandans based in eastern Congo, Chenard said.

Those insurgents, including members of the former Rwandan army and extremist Interahamwe militia (search), have been based in eastern Congo since leading the 1994 genocide in Rwanda.

Sunday's ambush came as fighters loyal to Gen. Laurent Nkunda withdrew from Bukavu, just four days after seizing the strategic eastern Congolese city from government troops.

The battle for Bukavu on Wednesday was seen as the most serious setback to the transitional government that was put in place after the country's 1998-2002 civil war. On Sunday, Nkunda left the city in a convoy of two vehicles accompanied by about a dozen troops.

"I'm out of here," Nkunda told The Associated Press as he left.

It was unclear if Sunday's ambush was related to the crisis in Bukavu, but it ensured further destabilization.

The bulk of Nkunda's forces pulled out of Bukavu on Friday, setting up camps at military barracks on the outskirts of the city after U.N. troops took charge of security. But dozens of his fighters remained to protect his commanders and key installations.

U.N. spokesman Sebastien Lapierre said Nkunda informed U.N. military commanders earlier Sunday that he would leave the city.

"MONUC (search) (the U.N. mission in Congo) welcomes the initiative," Lapierre said. "We are carefully monitoring the situation to see if that is true."

Nkunda said his troops would move to Kavumu, a small town 22 miles north of this city. But a second renegade commander, Col. Jules Mutebutsi, said his troops would remain in the city, an important trading center on the border with Rwanda.

Mutebutsi said his fighters — who fought alongside Nkunda's forces — would be quartered in camps while efforts were made to resolve the crisis.

During the civil war, Nkunda and Mutebutsi were commanders in the main rebel group, the Congolese Rally for Democracy, which joined the transitional government when it was set up last June.

Also on Sunday, Belgian Foreign Minister Louis Michel left for Congo hoping to ease tensions. Belgium was the colonial ruler until Congo achieved independence in 1960. Brussels maintains close ties.

"Above all this is about trying to safeguard the transition process, which is clearly in peril," Michel told RTBF radio.

Belgium, the former colonial ruler of Congo, has sought to maintain close ties.

An estimated 3.3 million people were killed — mainly through war-induced disease and hunger — in the conflict in Africa's third-largest nation, which drew in at least six foreign armies after it erupted in August 1998.

Most of Congo has been relatively peaceful since the transitional administration took office, but eastern and northeastern Congo have remained volatile.

Both Nkunda and Mutebutsi were integrated into the national army, but later fell out with their commanders. Nkunda claims he has more than 4,000 troops, while Mutebutsi is estimated to have several hundred fighters.

They say they launched their assault Wednesday because the regional military commander assigned by the Kinshasa government — Brig. Gen. Mbuza Mabe — was persecuting members of a Tutsi community, the Banyamulenge. Both renegade commanders are members of Congo's Tutsi community.

Mutebutsi, who was based in Bukavu when he was integrated into the national army, said he was staying because his fighters belonged there as part of the army.

"I've put my troops in ... camps like I was originally asked to," Mutebutsi told the Associated Press. "This our home and there's nowhere else for us to go."

The government has accused Rwanda of being behind uprising. Rwanda has denied the accusations. On Sunday, Rwandan Foreign Minister Charles Muligande said Rwanda had closed its border with Congo because of Kinshasa's accusations.

Residents blamed Sunday's attack on Rwandan assailants.

"The assailants hid in the cover of the forest along the road and opened fire on the two trucks (marked) with the U.N. insignia," Chenard.

There were 30 South African peacekeepers in the U.N. trucks and they returned fire, but did not pursue their attackers, Chenard said.

Other peacekeepers who arrived on the scene shortly after the attack said "there were trails of blood going deep into the forest," Chenard added.

During the civil war in Congo, Rwanda backed the Congolese Rally for Democracy.