The attack, in the Nana-Mambéré prefecture, was allegedly carried out by the Return, Reclamation and Rehabilitation (3R) armed group, said a UN statement condemning the attack.
Central African Republic has been rocked by violence since 2013 when mainly Muslim Selaka rebels ousted then president Francois Bozize, prompting reprisals from mostly Christian militias. UN peacekeepers were deployed in 2014.
Violence waned after a peace accord was signed in February 2019 between the government and 14 armed groups including the 3R, following talks in Khartoum. But like previous agreements, this one has shown signs of falling apart.
Conflict in the Central African Republic has uprooted more than one million people, the United Nations has said.