Abidjan, Ivory Coast (CNN) -- Ivory Coast security forces loyal to incumbent President Laurent Gbagbo used tear gas and fired into the air to disperse supporters of Alassane Ouattara, authorities said Saturday.
Casualties could not be confirmed.
The international community has pressed incumbent Gbagbo to relinquish power to Ouattara, who foreign powers say won the election.
Hundreds of pro-Quattara supporters gathered on the first day of rallies calling for Gbagbo's ouster when the security forces moved in, said police Lieutenant Djedje. Ouattara has likened the planned mass protests to those in Egypt.
Gbagbo has imposed a curfew until Monday morning.
Saturday's clash occurred 48 hours before the arrival in Abidjan of the five heads of state designated by the African Union to find a "binding decision" to the Ivory Coast election standoff.
Before traveling to Ivory Coast, the heads of state will first hold a meeting in Mauritania on Sunday. They will review the report by a team of experts, whom they sent early this month in Abidjan to work with the parties at stake in the conflict.
Chaired by Mauritanian President Mohamed Ould Abdel Aziz, the panel includes Jacob Zuma from South Africa, Blaise Compaore from Burkina Faso, Jakaya Kikwete of Tanzania and Idriss Deby Itno of Chad.
Two leading Ivory Coast banks closed their doors, raising fears that a money shortage will worsen the crisis in the West African nation. Mounting security concerns prompted BICICI and Citibank to suspend operations Monday.
Ivory Coast has been in crisis since a late November election that ended in dispute.
The political standoff in the country has raised fears of a renewal of the bloodshed suffered after a civil war broke out in 2002.
More than 33,000 people have fled to neighboring Liberia since the crisis began; 20,000 more have been internally displaced, according to the United Nations.