Security remained so precarious that Red Cross teams could not venture into the streets to collect bodies for burial.
"For the moment, no one dares to go out as everything suggests that fighting can resume at any time," said the Rev Gildas Gbeni of the St. Louis Catholic mission in Bria.
"Witnesses coming from different neighbourhoods say they have had to climb over dozens of bodies that now litter the ground."
Witnesses said the fighting erupted early yesterday between the anti-Balaka militia and rebels from the group known as FPRC who were once part of the Seleka movement.
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The peace deal signed Monday in Rome among nearly all of the country's armed groups had called for an immediate cease- fire. Many were skeptical, however, because previous agreements had quickly failed.
Central African Republic has faced deadly interreligious and intercommunal fighting since 2013, when predominantly Muslim Seleka rebels seized power in the capital, Bangui. Mostly Christian anti-Balaka militias fought back, resulting in thousands of people killed and hundreds of thousands displaced.
Bria has seen repeated clashes since May, leaving dozens dead. An estimated 41,000 people there have fled for their lives.