The Central African Republic's capital was rocked by deadly overnight clashes hours before France's defence minister formally ended a military operation there Monday, hailing it as a "success".

Local sources said about 10 people had been killed in a settling of scores between armed groups Sunday night in the restive Muslim PK5 neighbourhood of the capital Bangui.

The toll had yet to be confirmed by the UN force MINUSCA -- which will be alone in facing the militia terrorising civilians now that France is ending its Sangaris operation, begun three years ago to halt mass killings in the former French colony.

"This does not mean the end of military relations between France and the Central African Republic," French Defence Minister Jean-Yves Le Drian said in a speech to parliament in Bangui on Monday.

"The French army will indeed be less visible but it will be present, active and vigilant. We're proud of Operation Sangaris, so it's out of the question to allow the gains to be put at risk," Le Drian told MPs fearful of renewed violence.

Residents were continuing to flee the area around PK5 on Monday, fearing further bloodshed. A helicopter from the international force circled over the city from dawn, an AFP correspondent said.

Renewed killings have shaken the country of 4.5 million people, spearheaded by rival Muslim and Christian militia groups. Many Central Africans are worried to see the French troops go, although the United Nations has deployed a force of more than 12,000 men.

The latest clashes came just after Le Drian arrived Sunday to wind up the mission launched at the end of 2013 to prevent a feared genocide after president Francois Bozize was ousted from power.

The French minister went into talks with the CAR's President Faustin-Archange Touadera, elected early this year once relative calm was restored, and met officials in MINUSCA.

He was due to attend the ceremony ending the Sangaris operation in the afternoon, but vowed that a "tactical reserve force of 350 soldiers" would remain. At its height, Sangaris was 2,500 strong.

- 'We stopped the mass killings' -

Earlier this month Le Drian told the French parliament that the Sangaris mission, backed by a UN mandate, had been "a success".

"We stopped the mass killings... allowed a process of intercommunal reconciliation, the reconstitution of the state, a presidential election, and legislative elections," he said.

Prominent CAR politician and former presidential candidate Anicet Georges Dologuele challenged Le Drian's optimism, stating that "Sangaris is pulling out far too early."

"Our security forces are not ready to take up the baton," Dologuele said. "The UN forces are more and more overwhelmed in their firefighting role."

"It's always too early," Le Drian countered. "These responsibilities are above all your own."

Two days before Le Drian's arrival, 25 people were killed in clashes in the centre of CAR, including six police officers. The government denounced the violence as a "Machiavellian plot designed by the enemies of peace".

UN vice secretary general Jan Eliasson is also expected in Bangui from Tuesday for a two-day visit, MINUSCA said.

One of the world's poorest countries, CAR has scarcely emerged from the chaos of civil war which erupted in 2013 following the overthrow of Bozize, a Christian, by Muslim rebels from the Seleka coalition who installed their own leader.

Armed groups have flourished over the years given the weakness of the state. Among the main culprits are factions from the mostly Muslim former Seleka rebel force, and the Christian "anti-Balaka" militias, a reference to the machetes used by the rebels.

There are also vigilante groups made up of nomadic, predominantly Muslim Fulani herders, as well as others specialising in highway robbery.

The conflict in CAR since 2013 has left thousands of people dead and forced 4.5 million to flee their homes.