Reports from the Central African Republic say at least 37 people have been killed in an attack on the northern town of Ndele.
Three rebel groups stormed the main market then attacked other parts of the town, setting up a base in a Catholic church.
United Nations peacekeepers and another militia, which previously controlled Ndele, failed to fight off the attackers.
Numerous rebel groups have been operating in the CAR since President Francois Bozize was overthrown seven years ago.