Amnesty International is calling for the rapid deployment of a robust UN peacekeeping force to the Central African Republic, with a clear mandate to protect civilians.
Amnesty claims almost 1,000 people have been killed in a two-day rampage by Muslim rebels Seleka in CAR. The two-day reprisal took place after the Christian anti-Balaka militia went door-to-door in some parts of Bangui and killed approximately 60 Muslim men.
Both Christian and Muslim groups are fuelling anger and revenge; many people have shown Amnesty International researchers photos and videos of slaughters that they keep on their mobile phones.
"Crimes that have been committed include extrajudicial executions, mutilations of bodies, intentional destructions of religious building such as mosques, and the forced displacement of massive numbers of people." explained Amnesty International's Central African expert Christian Mukosa.
"This is the situation: you have people who knew each other for a long long time killing each other; using machetes to make less noise."
Amnesty's senior crisis adviser Joanne Mariner added: "Both Seleka and anti Balaka systematically attack the civilian population.
"The international community has an important role to play in the Central African Republic, ensuring peacekeeping forces are deployed with all haste and are given the resources they need to prevent even greater bloodshed.
"The international community can also help by ensuring that atrocities are independently and impartially investigated, so that individual perpetrators - not entire communities - are held accountable for their crimes."
Human Rights Watch, which is publishing a separate report focusing on the escalation of sectarian violence, said that the Christian militia cut children's throats and forced their parents to watch the slaughter.
The African Union has promised to deploy up to 6,000 troops in a new peacekeeping force, which is due to take authority in the Central African Republic on 19 December.