CRISIS IN CENTRAL AFRICA : Rwandan Rebels Take Airport, Key Army Base : Africa: Kigali remains closed to air traffic, choking off relief supplies, U.N. reinforcement. Truce called to allow envoy’s visit.

Rebels captured strategic positions Sunday in their drive to take Rwanda’s capital, overrunning the international airport and a nearby military base outside Kigali as government troops fled.

After weeks of ferocious fighting, the momentum swung decisively in favor of the Rwandan Patriotic Front, which could use the two important posts on the western outskirts of the capital to launch new assaults.

The capital’s airport--which the rebels took hours before seizing the key Kanombe army barracks--is the devastated city’s main lifeline for urgently needed relief supplies, but it remains closed to U.N. reinforcements or supplies.

No one knows when it will be safe to use it.

Rebels have said they would welcome a resumption of U.N. relief flights, but U.N. officials were still trying Sunday to negotiate a deal with both warring parties for uninterrupted use of the airport.

“We still need an agreement from both sides because our planes would still have to fly over areas controlled by government troops,” said Maj. Jean-Guy Plante, a U.N. spokesman.

Government troops “still have a capability to bring down our planes,” said Abdul Kabia, a U.N. spokesman in Kigali. “When they moved out of Kanombe, they took antiaircraft guns with them.”

The United Nations also hopes to use the airport as a staging area for 5,500 new peacekeepers authorized by the Security Council last week. If it can’t, officials said they would have to find an alternate site.

The rebels are predominantly members of the minority Tutsi tribe, while the majority Hutus control the government and the military. The bloodletting began a day after President Juvenal Habyarimana and Burundi President Cyprian Ntayamira--both Hutus--were killed in a suspicious plane crash in Kigali on April 6.

The Hutu presidential guard, some army units and gangs organized by extreme Hutu politicians slaughtered mostly Tutsi civilians and Hutus considered government opponents.

At least 200,000 people are estimated to have died in massacres that quickly spread throughout the mountainous country.

Government forces offered little resistance Sunday to the assault on the airport, U.N. spokesman Kabia said.

“The rebels came running from all directions, and the soldiers just vanished,” another U.N. official said, speaking on condition of anonymity.

Rwandan army Chief of Staff Gen. Augustin Bizimungu said his troops evacuated the airport and the barracks at the United Nations’ request. He denied that the airport and barracks were “captured.”

“We shall organize ourselves and continue fighting,” he told French radio.

U.N. officials said they doubted that the rebels would try to take the city’s downtown, swarming with armed militiamen backing the army.

Officials said Brig. Gen. Romeo Dallaire, the Canadian U.N. military commander, had arranged a truce to allow a visit today by special U.N. envoy Iqbal Riza.

Riza plans to discuss with the warring parties the deployment of the new, largely African peacekeeping force.

“Government and rebel forces have agreed to a truce while U.N. envoys are in the country,” Dallaire said. “Let’s hope they obey it.”

U.N. spokesman Plante said the whereabouts of three government battalions from the Kanombe camp was unknown, “and the possibility of them regrouping for a counterattack cannot be ruled out.”

Plante said the United Nations was also trying to decide what to do with an estimated 1,600 civilians, mainly women and children, who fled the Kanombe military camp and had gathered without food at the airport.

Officials in neighboring Uganda on Sunday declared that three districts bordering Lake Victoria were disaster areas because of the danger posed by thousands of corpses that have floated downriver from Rwanda.

Radio Uganda said 10,000 to 40,000 corpses have floated into Lake Victoria from the Kagera River, which has its source in Rwanda’s highlands. It said the government had appealed for international help in disposing of the bodies. Many bodies appeared to be mutilated, and some were bound.