It is impossible to confirm the accuracy of the reports circulating about Colonel Yugo. But missionaries and local hospital authorities said he killed at least eight people in the city, including the two pastors, a local alderman and five young boys in a market.

''It's no secret that he's killed a lot of people personally,'' said Gerald Selenke, a Catholic missionary. ''He's evidently a very deranged individual.''

Atua Benjamin, the director of Kabundo General Hospital, said: ''They simply sowed terror here. The mercenaries assumed everyone who was young was a rebel and had to be killed.''

Colonel Yugo's origins are mysterious. Like most of the mercenaries who arrived in Kisangani in January, he was a Serb and had apparently fought in Bosnia. Most of the mercenaries preferred not to talk about their pasts, residents said.

The colonel is described as tall, over 6 feet 2 inches, with a muscular build, dark hair and dark eyes. Residents said he appeared to be about 40.

On one occasion he threatened to shoot two journalists who dared to walk into his headquarters at the airport. ''He was the kind of man who could do you serious harm with a smile,'' Mr. Mwanatambwe said.

Mr. Mwanatambwe, a beef importer from Goma, said he was arrested by the mercenaries in the middle of the night of Feb. 23, along with four friends. They were taken by truck to the airport, where they were imprisoned with several other men. No one ever gave an explanation for their detention, but later they learned that the mercenaries had accused them of spying for the rebels, he said.