The African peacekeeping force in the Central African Republic said it will now treat the anti-balaka militia groups as "enemies."
General Jean-Marie Michel Mokoko, who heads the international force known as MISCA, made the comment to a radio station in Bangui late Tuesday, about 24 hours after a peacekeeper was shot and killed by gunmen in Boali, 80 kilometers north of the capital.
MISCA said other peacekeepers returned fire and killed 12 assailants who were later identified as anti-balaka.
In a statement, Mokoko said anti-balaka have "systematically targeted MISCA vehicles and personnel" and "identified themselves as spoilers and enemies of peace in the C.A.R."
He said MISCA is determined to neutralize "all illegal armed groups."
The largely Christian militias have attacked and looted Muslim neighborhoods in Bangui and other towns, forcing tens of thousands of Muslims to flee to protected areas or neighboring countries.
The anti-balaka - whose name means "machete proof" or invincible - formed last year in response to a wave of killing and looting by mostly Muslim Seleka rebels.
Mokoko told the radio station that the militias will not be treated as self-defense groups.
MISCA, which is sponsored by the African Union, has about 6,000 troops in the C.A.R., working alongside 2,000 French troops in efforts to disarm militias.
The peacekeepers have been largely unable to stop the anti-balaka from surrounding and attacking Muslim communities.
Medical aid group Doctors Without Borders says there was heavy gunfire and explosions over the weekend in Bangui's PK5 and PK12 neighborhoods, where thousands of Muslims have been trapped for weeks.
The group says it treated 38 people for wounds caused by bullets, grenades and machetes. It says three of the patients died.