Amnesty called for a UN peacekeeping force.
The group noted that war and crimes against humanity were being committed in the country, and warned of a surge in sectarian violence.
The Central African Republic is about the size of France and a country rich in resources, including diamonds, gold, timber and ivory, but it has rarely seen political stability or economic growth in the 53 years since it gained independence.
Christian Mukosa, the Amnesty International’s Central Africa expert said crimes being committed include extrajudicial executions, mutilation of bodies, intentional destruction of religious buildings and forced displacement of massive numbers of people.
He noted that CAR had seen violence and chaos since the Muslim-backed Seleka militia and other rebel groups from the marginalised northeast seized the capital Bangui in March.
“President Francios Bozize fled to Cameroon, and Michel Djotodia, who had been one of the Seleka leaders, made himself President,’’ he said.
Mukosa therefore called for the deployment of a “robust” UN peacekeeping force, with a mandate to protect civilians, and enough resources to do so effectively.
He added that “the UN Security Council needs to act quickly to bring this evolving catastrophe to a halt.
“The continuing violence, the extensive destruction of property, and the forced displacement of the population in Bangui are feeding enormous anger, hostility and mistrust.’’
He warned that there could be no prospect of ending the cycle of violence until the militias were disarmed, with proper and effective protection for the thousands of civilians at risk in the country.
Mr. Mukosa said that residential neighbourhoods must be made safe as an urgent priority in order to allow people to go back to their homes and resume their normal lives.