"The plight of civilians in CAR since September 2012 has gone from bad to worse," ICC prosecutor Fatou Bensouda said in a statement on Friday. Bensouda added she had received recent reports of "extreme brutality" by various groups.

"The allegations include hundreds of killings, acts of rape and sexual slavery, destruction of property, pillaging, torture, forced displacement and recruitment and use of children in hostilities," she said. "In many incidents, victims appear to have been deliberately targeted on religious grounds."

The Hague, Netherlands-based court has had a separate investigation underway in the Central African Republic since 2007. The preliminary investigation announced on Friday could lead to a second investigation if prosecutors find enough evidence.

Violence against Muslims, who have been brutally killed or mutilated and seen mosques set on fire, has escalated in recent weeks.

The primarily Muslim armed opposition alliance Seleka overthrew Christian President Francois Bozize in March 2013. His Muslim successor, Michel Djotodia was pressured to cede power to Catherine Samba-Panza, but the newly elected interim president has been unable to curb the unrest.

Thousands of people have been killed in sectarian violence over the last 13 months and one million have been displaced.

dr/ph (AP, Reuters, dpa)