The U.N. refugee agency says up to one million people have fled their homes in Ivory Coast because of post-election violence.
Spokeswoman Melissa Fleming told reporters on Friday the mass flight is being fueled by “fears of an all-out war.”
The agency estimated that between 700,000 and one million people have been displaced, mostly from the commercial city of Abidjan.
Abidjan has been the scene of fighting between supporters of rival presidents who are struggling for power.
A coalition of 32 international groups said Friday the humanitarian situation in Ivory Coast has reached a “critical level.”
Incumbent president Laurent Gbagbo has refused to turn over power to Alassane Ouattara, the internationally recognized winner of a November presidential election.
The U.N. Security Council is set to consider the political crisis during a meeting in New York on Friday.
On Thursday, a group of West African leaders urged the United Nations to strengthen its peacekeeping mandate in Ivory Coast and impose sanctions on Mr. Gbagbo.
The 15-member Economic Community of West African States also called on the U.N. mission in Ivory Coast to help with the transfer of power from Mr. Gbagbo to Mr. Ouattara.
The United Nations says at least 462 people have been killed in violence since the crisis began.