French army copters fired on a military camp held by the army loyal to Cote d'Ivoire's Gbagbo on Monday in Abidjan, media reported.
A separate report quoted witnesses as saying that the UN helicopters also fired on pro-Gbagbo military camp in Abidjan.
The attack occurred as the camp headed by the country's internationally recognized President Alassane Ouattara declared the final battle to take over control of the world's top cocoa producing country in West Africa.
French President Nicolas Sarkozy has allowed French force to participate the military operation in Cote d'Ivoire with UN security force to prevent the forces of Ivorian strongman Laurent Gbagbo from killing civilians, according to a statement issued by the presidency on Monday night.
In a letter addressed to Sarkozy and published by the Elysee Palace, the UN Secretary-General Ban Ki-moon demanded the support of French troop stationed in Cote d'Ivoire to "neutralize the heavy weapons used against civil population and the personnel of the United Nations in Abidjan."
In responding UN chief's request, Sarkozy said in a published replying letter that "I confirm you that I have authorized French force ... to carry out the operation jointly with UNOCI."