Seleka fighters briefly seized power in the majority Christian country of 4.5 million in 2013 and later handed power over to an interim government.
French and U.N. troops halted a rebel march towards the capital of Central African Republic this week, clashing with mostly Muslim fighters about 180 km (110 miles) northeast of Bangui, a government spokesman said.
Dominique Said Paguindji and residents said the troops fought the Seleka rebels on Saturday in the town of Sibut after an ultimatum for them to halt their march southwards expired.
It was not immediately clear if there were any dead or wounded during the clashes.
The former French colony has been torn by bloodshed since 2013 and interim authorities are struggling to disarm militias ahead of elections scheduled for Oct. 18.
Seleka fighters briefly seized power in the majority Christian country of 4.5 million in 2013 and later handed power over to an interim government. However, they still control large swathes of Central African Republic's north.
The international community is pressing for Central African Republic to go ahead with an election intended to restore democratic governance by the end of this year, despite widespread lawlessness.
But in a blow to the timetable, the president of Central African Republic's election commission said he was resigning this week.
The United Nations Office for the Coordination of Humanitarian Affairs confirmed this weekend that 77 people were killed and more than 400 injured in a surge of violence in Bangui that began in late September.