A hospital employee said that French troops and Congolese soldiers from African Union peacekeeping force MISCA were "ambushed" outside the hospital in the central mining town of Bria while making their way back to their airport base night.
Gunfire broke out for around half an hour outside the hospital in the town centre, according to the employee, who asked not to be named.
International peacekeeping troops are in the area in a bid to stop months of violence between the country's Christian majority and Muslim minority.
The crisis began when a mostly Muslim rebel group called Seleka seized power a year ago and some of its members went rogue, attacking the civilian population and sparking revenge attacks by Christian vigilante groups.
Both sides have been accused of brutal violence against civilians, and about a quarter of the country's 4.6 million people have fled their homes.
Sebastien Isern, a communications officer for the French force in the capital Bangui, confirmed incident.
"We have been attacked by an armed enemy group," he told AFP. "We did not have any fatalities, but two soldiers from the MISCA force have been injured," he said, without giving further details of the nature of their injuries.
He said the situation remained "complex and volatile".
Speaking for Seleka, General Moussa Dhaffane told AFP that the French army had started the hostilities. "One of their helicopters fired on the vehicle of one of our commanders in the area," he said.
"We have no problem with France, it is a problem of method. There is a crisis of confidence between Sangaris (the French peacekeeping force) and Seleka," he said.
Earlier, when foreign troops rolled into the town, which is 400 kilometres (250 miles) from Bangui, they were stoned by Muslim youths, according to a teacher reached by telephone.
The teacher blamed the stone-throwing on "young Muslims manipulated by Seleka".
He said one young man was killed in the incident but provided no further details.
Tension was high in Bria Friday, with shops closed while youths armed with knives roamed the streets, residents told AFP.
The French force, now 2,000 strong, was first deployed in December and is working alongside the African Union force to try and keep the peace.
Initially deployed in the south and centre of the landlocked nation, the foreign troops have started to move eastwards and towards the northern border with Chad and Sudan. They are heading into territory where Seleka fighters fell back after being chased out of Bangui.
The ethno-religious conflict has led to international warnings of a potential genocide, but it is unprecedented in a nation where Muslims and Christians formerly lived peacefully together through coups, army mutinies and general strikes.
With concerns mounting, the UN Security Council voted to send some 12,000 UN peacekeepers to the country, including up to 10,000 military personnel and 1,800 police. This force is intended to take over from the French and AU missions, but not until .
The European Union has meanwhile pledged to send 800 troops.