The African peacekeeping force in the Central African Republic declared war on the majority-Christian vigilante groups known as "anti-balaka" on Wednesday after a fresh outbreak of deadly violence in the capital Bangui.

The head of the MISCA force blamed the groups for recent attacks on peacekeepers in the former French colony, and said they would be treated as "enemies".

At least 18 people have been killed in the Central African Republic capital of Bangui since Saturday as a result of clashes involving armed groups and foreign peacekeepers, medical staff and residents said Tuesday.

"At least 15 bodies have been picked up by Red Cross volunteers at the scene of the fighting," on the outskirts of the commercial PK-5 district, a Central African Red Cross official told Agence France Presse, asking not to be named.

Christian and Muslim leaders from conflict-torn Central African Republic said Monday they have appealed to U.N. chief Ban Ki-moon to rapidly deploy peacekeepers to stop the country's "descent into hell".

A multi-faith delegation, made up of an archbishop, an imam and the head of the country's Protestant community, made the plea during a 10-day visit to Washington and New York, where they also sought help from the United States to end months of Christian-Muslim violence.

At least four people have been killed in clashes between armed groups and international peacekeepers in the capital of the strife-torn Central African Republic, a military official said Sunday.

A further seven people were injured when violence erupted Saturday in the PK-5 district of Bangui between Christian militia and Muslim groups, said an officer with the African Union military force known as MISCA.

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The U.N.'s rights chief on Thursday expressed horror at the level of violence in the Central African Republic, citing cannibalism, child decapitations and gruesome lynchings.

U.N. High Commissioner for Human Rights Navi Pillay warned that the world's response was alarmingly slow and made a passionate appeal for greater mobilization.

The French commander of a European Union peacekeeping force which had been due to deploy in the Central African Republic this week said Wednesday he did not have enough soldiers.

"The deployment hinges on the creation of a logistical unit of around 100 forces," General Philippe Ponties told French radio RFI, describing the shortage of volunteers as "worrying".

African peacekeepers on Monday announced the seizure of a large weapons cache near Bangui airport in the capital of the strife-torn Central African Republic.

"This is an important arsenal that would be enough to keep a large part of Bangui under siege," said a source in the MISCA force who asked to remain anonymous.

Dozens of Central African refugees have died from starvation and many more are seriously ill from hunger and exhaustion after fleeing the conflict-ravaged country for Cameroon, the U.N. warned Friday.

Nearly 50 people, at least 33 of them children, have died from severe malnutrition after reaching Cameroon in the first two months of the year, said a spokeswoman for the United Nations' refugee agency UNHCR.

France warned on Friday that the launch of a much-needed EU military operation in conflict-ridden Central African Republic planned for next week may not take place for lack of troops.

"If additional efforts are not made rapidly, it won't be possible to launch as planned this essential operation next week," French Foreign Minister Laurent Fabius and Defense Minister Jean-Yves Le Drian said in a joint statement.