Hundreds of U.N. peacekeepers are based in a town where there are reports of human rights abuses and mass killings. A Catholic charity said attackers with machetes and guns killed as many as 1,000 people.
The fighting comes as the former president of the Ivory Coast, Laurent Gbagbo refuses to step down after losing an election.
The candidate who did win the election, Alassane Ouattara says fighters are preparing a final push to depose the entrenched incumbent leader.
Saturday, Gbagbo called on his supporters to descend into the streets to form a human shield around the presidential palace. Boatloads of youth were ferried into the center of town and have been coursing the streets carrying rudimentary weapons such as two-by-fours and metal bars.
Ouattara's camp reports that the vast majority of the military has defected to his side, leaving only a small contingent of fighters to defend Gbagbo.
Thousands of pro-Ouattara troops amassed on the city's northern edge Sunday.
The Associated Press contributed to this report.