At least 800 people have been killed in the western Ivory Coast city of Duekoue this week, the International Committee of the Red Cross (ICRC) has said.
They died in inter-communal violence in one district of the city, it added.
The head of the ICRC delegation in the country said the event was particularly shocking in its scale and brutality.
Fighting has continued in Abidjan between forces loyal to the UN-recognised president Alassane Ouattara and the incumbent, Laurent Gbagbo.
Mr Ouattara was internationally recognised as president last year after the electoral commission declared him the winner of a November run-off vote, but Mr Gbagbo also claimed victory and refused to leave office.
‘Fearing for their lives’
The ICRC said delegates and volunteers from the Ivorian Red Cross had visited Duekoue on Thursday and Friday to gather evidence of the killings, which are believed to have taken place on Tuesday.
There is no doubt that something on a large scale took place in this city, on which the ICRC is continuing to gather information,” ICRC spokeswoman Dorothea Krimitsas told the AFP News agency.
She said the Red Cross representatives had “themselves seen a very large number of bodies”. They took 28 bodies to the local morgue and more would be removed in the coming days, she added.
“Everything seems to indicate that this was inter-ethnic violence.”
The head of the ICRC delegation, Dominique Liengme, said in a statement: “This incident is particularly shocking in its size and brutality.”
“The ICRC condemns direct attacks on civilians and reminds the parties to the conflict to make sure that people in the territory under their control must be protected under all circumstances,” she added.
The Geneva-based organisation said tens of thousands of women, men and children had fled fighting in Duekoue since Monday.
The city lies on a strategic crossroads in the west of Ivory Coast and has been under the control of forces loyal to Mr Ouattara since Tuesday.
The International Organisation for Migration (IOM) said many Duekoue residents were heading to the nearby town of Guiglo “fearing for their lives”.
Gbagbo ‘going nowhere’
The national army has put up almost no resistance since Mr Ouattara’s supporters launched an offensive to oust Mr Gbagbo on Monday, sweeping down from the north to capture the capital, Yamoussoukro, and the key port of San Pedro.
However, they have been unable to defeat those still loyal to the former president in parts of Ivory Coast’s main city, Abidjan.
There have been fierce clashes outside the presidential palace and the headquarters of state television in the upmarket district of Cocody. Fighting has also been reported in Plateau and Agban areas.
