The United Nations and the government in the Central African Republic say rebels have carried out two attacks near the capital Bangui.
Local reports said one of the assaults targeted a checkpoint manned by government troops and Russian mercenaries.
Ministers say the attackers were pushed back, but a UN spokesman has been quoted as describing the fighting as ongoing.
The US embassy says it’s received reports of clashes in the city and in Bimbo to the west of it.
Rebel forces, opposed to the re-election of Faustin-Archange Touadéra and supported by former President François Bozizé, have been advancing on the city.