UN troops and an armed group exchanged gunfire during the night near the president's residence in the Central African Republic, a security source told the AFP news agency.
It came hours after at least two people were killed when the the UN and central African forces targeted armed groups in a mainly Muslim district of Bangui, UN sources told AFP.
Eight people belonging to the armed groups Force and 50/50 had been detained by the UN peacekeeping force and ammunition had been seized, a spokesman for the UN official Herve Verhoosel told AFP.
The Central African Republic has been unstable since the mainly Muslim Seleka rebels overthrew the government in 2013.
It handed power to a transitional government in 2015, as the country descended into religious and ethnic conflict.