Christian militiamen attacked a Central African army base in the capital Bangui Tuesday, as French and African soldiers struggled to contain sectarian violence.
Vigilantes attacked a military position at the PK-11 crossroads on the northern outskirts of Bangui, General Mahamat Tahir Zaroga told AFP.
He said the attack, the second in as many nights by the so-called anti-balaka groups, caused no casualties.
Gunfire rang out through the night in Bangui, where 1,600 French troops and around 4,000 African peacekeepers are attempting to curb escalating religious strife.
Witnesses holed up in their homes reported exchanges of fire in the central Ben Zvi neighbourhood just before dawn.
The vigilantes were formed in response to abuses perpetrated by demobilised rebels from the Seleka coalition that helped Michel Djotodia become the country's first Muslim head of state after a March 2013 coup.
Around 100,000 people displaced by weeks of violence have sought refuge near the main French army base by Bangui airport.
The UN children's agency on Monday warned about "unprecedented" levels of violence against youngsters in the country, saying at least two children had been beheaded.
"More and more children are being recruited into armed groups, and they are also being directly targeted in atrocious revenge attacks," said the UNICEF representative in Central Africa, Souleymasne Diabate.
Several hundred people staged a demonstration Tuesday to protest against attacks they said were carried out by rogue Seleka gunmen in the Don Bosco district of the capital.
The mostly Christian families urged France, the former colonial power, to step up its operations to disarm Seleka warlords who have yet to be flushed out of Bangui.
The tit-for-tat violence by Seleka groups and Christian vigilantes is believed to have killed more than 1,000 people this month.
Humanitarian groups said last week they needed $152 million to help save lives and ensure the protection of 1.2 million people in the country during the next three months.
French forces and the African peacekeeping outfit MISCA received a UN mandate in early December to restore order in the chronically unstable country.
The chaos that set in after Djotodia's coup sparked international fears of a major civil conflict.