* Witnesses say Chadians among Muslim fighters-U.N. team
* French tactics made some disarmed fighters vulnerable
By Tom Miles
GENEVA, Jan 14 (Reuters) - A U.N. human rights team has gathered testimony that Chadian citizens, including peacekeepers, carried out mass killings during chaotic violence in Central African Republic, the U.N. human rights office said on Tuesday.
The team also found that French peacekeepers' disarming of some Muslim fighters had the unintended side-effect of enabling their Christian enemies to kill them and their families in retaliatory attacks. French tactics subsequently changed.
U.N. human rights spokesman Rupert Colville said the evidence showed that intercommunal hatred had risen to "extraordinarily vicious levels". Neighbouring Chad has denied helping the Muslim fighters.
A Muslim rebel coalition, Séléka, seized power in Central African Republic last March, unleashing a wave of killings and looting that in turn sparked revenge attacks by the "anti-balaka" Christian militia.
The Séléka leader-turned-president Michel Djotodia resigned last Friday under intense international pressure, but sporadic violence has continued, despite the presence of 1,600 French troops and 4,000 African Union peacekeepers.
The crisis has sent food prices soaring, leaving many households down to one meal a day and 2.6 million people in need of U.N. humanitarian assistance, the U.N. World Food Programme said in a separate report on Tuesday.
The four-person U.N. human rights mission carried out 183 interviews between Dec. 12 and Dec. 24, mainly collecting testimony on a wave of violence since Dec. 5, including summary executions, sexual violence, torture, disappearances, looting and burning of churches and mosques.
"Numerous interviewees identified the ex-Séléka perpetrators as being Chadian nationals," their report said.
"Witnesses consistently reported that ex-Séléka wearing the armbands of Chadian FOMAC (peacekeepers) went from house to house searching for anti-Balaka, and shot and killed civilians, including children, women, elderly and disabled civilians."
The team also heard multiple accounts of collusion between FOMAC and ex-Séléka forces.
One source reported that ex-Séléka, jointly with Chadian FOMAC, on Dec. 5 went "door-to-door looking for anti-Balaka and indiscriminately killing at least 11 people, including elderly women, sick persons, and persons with mental disabilities."
The team's report is the first batch of evidence collected by the United Nations, which is setting up a formal Commission of Inquiry to collect and investigate human rights abuses, and is a first step towards potential prosecutions.
The country's new interim leader Alexandre-Ferdinand Nguendet ordered his troops to shoot troublemakers "at point blank range" on Monday, but U.N. human rights chief Navi Pillay warned in a statement that the government must not commit further breaches of international human rights law.
The U.N. team also received reports that French disarmament of ex-Séléka forces left Muslim communities vulnerable.
Colville, the U.N. human rights spokesman, defended the French peacekeepers.
"They were obviously trying to disarm armed men, which was a good thing. There were anti-balaka elements or even civilians who took advantage of that to attack and kill people who had been disarmed, or their dependants.
"So I think obviously it wasn't foreseen but I believe the tactics have changed since it became apparent that that was happening."
The U.N. human rights committee will hold a special session to debate the situation in Central African Republic next Monday and is also likely to appoint a dedicated investigator.