Ivory Coast warlord Ibrahim "IB" Coulibaly was badly beaten before being shot in the chest, his spokesman said.
Felix Anoble confirmed that photographs posted on the internet of a bloody-faced man with an apparent bullet wound to the heart showed 47-year-old Coulibaly after he was killed on Wednesday night.
A commander for defence minister Guillaume Soro had said Coulibaly appeared to have killed himself rather than surrender when troops seized Coulibaly's stronghold in Abidjan. Mr Anoble denied Coulibaly had committed suicide.
"Did you not see the photograph?" he asked. "That's him. His face is all swollen because they beat him badly before delivering the final shot."
Ivory Coast's President Alassane Ouattara, whom Coulibaly had said he considered "a father" on Thursday expressed his regrets at the death of his wife's one-time bodyguard, who began the pro-democracy battle for Abidjan that put him in power.
A photograph posted at the news website www.abidjan.net showed the body of a man, arms stretched above him, with an apparent bullet wound to the chest and a bloodied face which looked like Coulibaly.
Mr Anoble said he was killed after his troops were attacked while waiting for United Nations peacekeepers to arrive and disarm them.
UN deputy spokesman Farhan Haq, speaking from New York, said the United Nations had negotiated a peace meeting and sent a patrol to escort Coulibaly. But when it arrived "Mr Coulibaly changed his mind and refused to come". Mr Haq said Coulibaly was attacked after the peacekeepers left.
Newly-installed President Ouattara gave no details about Coulibaly's death, saying only "things happened as reported in the media".
Mr Ouattara also announced that he would be inaugurated on May 21 in the administrative capital of Yamoussoukro. He won a November presidential poll but was unable to take command because strongman Laurent Gbagbo refused to cede power, plunging the West African nation into four months of chaos.