Fighters for Alassane Ouattara, the recognized winner of last year's presidential election attacked the presidential palace held by incumbent Laurent Gbagbo, the BBC reported. But Gbagbo's troops appeared to have recaptured the state television station, RTI.
The situation in Abidjan was murky, with Gbagbo's soldiers defending a base reported to be fighting each other.
The fighting in an Abidjan suburb included an attack by forces loyal to Laurent Gbagbo on U.N. peacekeeping forces, the United Nations said in a statement. Five of the Gbagbo soldiers were shot during the firefight but no U.N. troops were wounded, the United Nations said.
The U.N. mission in Ivory Coast issued a statement saying it "wishes to remind all concerned that its peacekeepers are operating under Chapter 7 of the United Nations Charter, which authorizes the use of force when under attack." U.N. mission added "it does not wish to have a confrontation with any of the Ivorian forces."
In Duekoue, recently taken by Ouattara's forces, at least 800 civilians were slaughtered in ethnic violence, the Red Cross said Saturday. The Catholic charity Caritas put the toll above 1,000.
Red Cross spokeswoman Dorothea Krimitsas told the Canadian Broadcasting Corp. Ivorian members visited the town on Thursday and Friday saw a "huge number of bodies."
"There is no doubt that something on a large scale took place in this city," she said.
Caritas spokesman Patrick Nicholson said workers visited Wednesday and saw victims killed by gunshot and machete wounds.
It was unclear which side was responsible.
The massacre brought the confirmed death toll since the November election to 1,300.
In Abidjan, an unidentified female Swedish United Nations peacekeeper and at least 500 people sought refuge with the French military, The Daily Telegraph reported.
Friday night, U.N. Secretary-General Ban Ki Moon reiterated the call for Gbagbo to step down.
"I renew my call on Gbagbo to step down to avoid further violence, and transfer power immediately to the legitimate winner of the election, President Ouattara," Ban said in Nairobi, Kenya.