A team from the International Criminal Court arrived in war-torn Central African Republic on Thursday on a first mission to investigate crimes committed in the country since bloodshed broke out in 2012.
"Serious crimes have been committed since 2012 in Central Africa," ICC head of international cooperation Amadi Bah said at a news conference in the capital Bangui.
A coalition of mainly Muslim rebels launched an offensive in late 2012 and eventually forced Francois Bozize out of power in March 2013.
Some of the fighters went rogue and the abuses they committed spurred majority Christians into creating vigilantes which have in turn carried out atrocities.
The daily looting, killing and raping sparked global fears of a new Somalia-style "failed state" in the heart of Africa and sparked the launch in December 2013 of a military operation by former colonial power France.
Thousands have been killed and around a quarter of the country's 4.6 million people displaced since the start of the fighting in the Central African Republic.
The ICC has already been investigating violence committed in the country more than a decade ago by the former vice president of the neighbouring Democratic Republic of Congo, Jean-Pierre Bemba.
"Since 2002, investigations have been carried out and they are continuing in The Hague with respect to the 2002-2003 crimes," Amadi Bah, the leader of the ICC tean in Bangui, said.
"Unfortunately, once again since 2012 serious crimes and unprecedented atrocities have taken place on Central African territory," he told reporters.
The ICC announced in February that it had opened an initial probe in the latest violence.
"My office has reviewed many reports detailing acts of extreme brutality... and allegations of serious crimes being committed," the court's chief prosecutor Fatou Bensouda said.
Her announcement came two days after a gruesome lynching that saw government soldiers stab, trample and pelt a suspected ex-rebel moments after a military ceremony attended by the new interim president.