African Union peacekeeping troops from Chad have clashed with demonstrators in the Central African Republic, near the airport in the capital Bangui.
According to protesters, one person was killed but that has not been confirmed.
The medical charity Medecins sans Frontières said about 40 people were treated for injuries, most of whom had been slightly hurt in a stampede as people panicked.
The clashes are complicating international efforts to calm inter-religious violence in large landlocked state, where France has deployed 1,600 troops to protect civilians.
Despite French pleas for the crowd to disperse, many among the capital’s majority Christian population accuse the troops from neighbouring Chad of siding with Muslim rebels.
One handwritten banner read “yes to France”, “no” to the Chadian force.
The Muslims from Seleka took power in a coup in March, installing their own interim head of state. Chadian peacekeepers were accused of standing aside.
In the latest clash witnesses said they reacted to stones being thrown by firing into the air – and the crowd.
In other developments, the European Union has banned the export of arms to the Central African Republic and mercenaries from being sent to the country.
France says the 28-nation EU will decide next month on a joint operation to help a French military intervention to stabilise the country.