The deaths are the first French combat losses since the country deployed troops to the West African nation last year.
The men were attacked on Monday near the central town of Sakassou, by rebels who appeared to be drunk, said a spokesman for the French army headquarters in Paris, Colonel Christian Battiste, on Tuesday.
A patrol of about 25 French soldiers had been chatting with local fishermen when a group of 15 to 20 former rebels arrived and started hurling abuse, said Battiste.
The French spokesman said the former rebels then started shooting. French soldiers returned fire. Two soldiers died of their wounds after being hit in the head and chest. A third was wounded in the foot.
French and regional peacekeepers are patrolling a frontline between the government held-south and the rebel-held north of Ivory Coast, following a civil war sparked by a failed coup in September 2000. Thousands of people were killed in the fighting.
France had a base in the West African state with about 600 troops prior to the outbreak of war. It deployed another 1000 soldiers in the following weeks before stepping up its ground force at the end of December with foreign legionnaires.
A spokesman for the Rebel New Forces said he had heard about the attack over the radio and investigations are underway.
Battiste said Monday’s gunbattle was an isolated incident, adding that the vast majority of the Rebel New Forces were co-operating with the peace effort.