In an especially grisly chapter of Ivory Coast's four-month conflict, hundreds of people have been killed in the western cocoa-producing town of Duekoue.
The International Committee of the Red Cross said 800 people were shot to death. The United Nations puts the death toll so far at 330.
Guillaume Ngefa, the deputy human rights director at the U.N. mission in Ivory Coast, blamed 220 of the deaths on forces loyal to Alassane Ouattara, the man recognized by the United Nations and other global powers as the rightful president of Ivory Coast. Ngefa said pro-Gbagbo forces killed 100 people.
The massacre occurred between Monday and Wednesday as Ouattara's Republican Forces led an offensive through the country to the commercial center of Abidjan, Ngefa said.
"We have evidence, we have pictures. This was retaliation," he said, referring to Ouattara's forces.
The Ouattara camp denied the accusations.
"The government firmly rejects such accusations and denies any involvement by the Republican Forces of Cote d'Ivoire (the French name for Ivory Coast) in possible abuses," it said in a statement.
"The government wishes to establish that the situation is quite the opposite," it said. "Forces loyal to former President Laurent Gbagbo, and its affiliated mercenaries and militias that have engaged in countless atrocities in western Cote d'Ivoire, during their flight before the advance of Republican Forces of Cote d'Ivoire."
Ngefa said so far, 320 bodies have been identified and the actual number could be much higher. He said the dead included civilians as well as mercenaries.
Before the Duekoue killings, human right monitors documented 462 deaths in the Ivory Coast conflict. This was the single bloodiest incident yet.
The International Committee of the Red Cross sent a team to Duekoue on Thursday and said most of the victims were civilians, said spokesman Kelnor Panglungtshan