THE HAGUE (AFP) - International Criminal Court prosecutor Fatou Bensouda said Friday she has opened an initial probe into "serious crimes" committed in the Central African Republic, the scene of spiralling sectarian violence.

"My office has reviewed many reports detailing acts of extreme brutality... and allegations of serious crimes being committed. I have therefore decided to open a preliminary investigation into this... situation," she said in a statement in The Hague.

The United Nation's refugee agency said Friday some 20,000 people have now fled to Cameroon to escape communal bloodshed in the country following a coup in March last year that ousted long-time leader Francois Bozize.

Rebels from the Muslim-dominated Seleka group seized the presidential palace in Bangui, forcing Bozize, who ruled for a decade, to flee.

The violence spiralled out of control when the ex-Seleka rebels went rogue and carried out atrocities against the Christian majority.

The campaign of killings, rape and looting sparked revenge attacks by Christian vigilantes known as "anti-balaka" (anti-machete).

Despite the presence of French and African peacekeeping troops, violence continues in the country, and has already forced about a quarter of the population of 4.6 million from their homes.

"The plight of civilians in CAR... has gone from bad to worse," Bensouda said.