French Defence Minister Jean-Yves Le Drian on Tuesday called on the international forces deployed in the restive Central African Republic to put an end to brutal attacks by the country's militias, "by force if needed".

"All militias who continue to be involved in mob violence and commit murder must stop," Le Drian said during a visit to Brazzaville in neighbouring Congo.

French troops and the African Union-led MISCA mission in the Central African Republic (CAR) must "implement the UN resolutions, by force if needed", he added.

Congolese President Denis Sassou Nguesso, who is a mediator in the conflict, said for his part: "It is the duty of the international community to act with more firmness and diligence to end the reign of barbarism."

The impoverished country descended into chaos last March after rebels overthrew the government, sparking deadly Christian-Muslim violence that has uprooted a million people out of a population of 4.6 million.

There are currently 5,300 AU troops on the ground in the former French colony and the force is expected to reach 6,000 by March.

France has deployed 1,600 troops, while the United States is providing logistical support.

In Washington on Tuesday, the US top diplomat for Africa, Linda Thomas-Greenfield, said "the French role in trying to bring about security and peace in CAR is very, very important."

She added that reports of brutal lynchings in the country "highlighted for me and others how urgent the situation is there".

Le Drian, who is on a tour of central African nations, said France would pursue its mission in the strife-torn nation with determination.

On Monday, the commander of French troops in the Central African Republic accused militia groups known as the "anti-balaka" of being the country's "main enemy of peace".

The mainly Christian vigilantes have been accused of brutal attacks against Muslims after the ouster of president Francois Bozize in March 2013 by mainly Muslim rebels led by Michel Djotodia, who resigned last month after failing to end the sectarian violence.

"Those who call themselves 'anti-balaka' have become the main enemy of peace in the Central African Republic," General Francisco Soriano said in a meeting in Bangui with the impoverished country's religious leaders, accusing the militia of inciting violence by "stigmatising" certain areas as Muslim.

The remarks came the day after a member of the country's transitional parliament, Jean-Emmanuel Ndjaroua, was gunned down in a drive-by shooting in the capital blamed on the anti-balaka.

On Saturday the head of the MISCA force, General Martin Tumenta Chomu of Cameroon, had also warned "outlaws" and "thugs" that his troops would put an end to their activities.

In a separate development, French troops on Tuesday uncovered a major arms cache, including explosives and ammunition, in a house in a northern Bangui stronghold of the anti-balaka militia.

Nothing is known about the owner of the weapons but they will be taken to a French camp and destroyed, a French military official said.

In the PK12 district in northern Bangui displaced Muslims and militias clashed late Monday, leaving at least seven people wounded, witnesses said.