The Hague - The International Criminal Court said it had opened an initial probe into war crimes in the Central African Republic, where another lynching on Friday underscored spiralling sectarian violence.
The latest victim fell off a lorry in a convoy of thousands of terrified Muslims fleeing Christian vigilantes in Bangui.
Residents hacked him to death and dumped his body on the road side, an AFP photographer saw, a killing observers say is only the tip of the iceberg.
On Wednesday, government soldiers stabbed, trampled and pelted a suspected ex-rebel in a gruesome lynching that took place moments after a military ceremony attended by the Central African Republic's new interim president.
France's 1 600 troops and the African Union's contingent of more than 5 000 have so far been unable to stem the sectarian violence which has displaced around a quarter of the population.
The ICC chief prosecutor's move to investigate the unrest that has plagued the nation of 4.6 million for more than a year brings yet another African case to the Hague-based tribunal.
"My office has reviewed many reports detailing acts of extreme brutality... and allegations of serious crimes being committed," Fatou Bensouda said in a statement.
"I have therefore decided to open a preliminary investigation into this... situation," she said.
9 000 fled
The UN refugee agency said 9 000 people, mostly Muslims, have fled to neighbouring Cameroon over the past 10 days alone.
Violence broke out in the poor landlocked country in late 2012 when a coalition of mainly Muslim rebels launched an offensive against Francois Bozize, who had been in power for a decade.
The Seleka fighters toppled him in March but some went rogue, killing, raping and looting in a bloody campaign their former leader Michel Djotodia - by then the country's first Muslim president - was unable to stop.
The violence drew comparisons with the warlords of Somalia and sparked revenge attacks by villagers who formed vigilantes known as "anti-balaka".
Former colonial power France deployed a force of 1 600 troops in December and thousands of African peacekeepers also began patrolling the capital but sectarian hatred boiled over.
The violence has in recent weeks "reached intolerable and unprecedented levels," the Doctors Without Borders group said in a statement on Friday.
"Civilians remain in constant fear for their lives, and have been largely left to fend for themselves," the charity's emergency co-ordinator Martine Flokstra said.
Wednesday's lynching, moments after the new interim president Catherine Samba Panza spoke of her pride in seeing the armed forces contribute to national security again, sent shockwaves across the international community.
In front of dozens of journalists who had covered the ceremony, uniformed troops ganged up on a suspected ex-Seleka rebel and beat him up.
One soldier dropped a huge block of concrete on the lifeless body as it was being dragged through the streets. The mob then burned the corpse and some posed for pictures in front of it.
'Bring them to justice'
"Honourable ministers, hunt them down and bring them to justice," the CAR's interim prime minister, Andre Nzapayeke, said at a press conference Friday.
"They are all over the Internet, they were parading in front of the cameras in a macabre spectacle. That means they can be identified," he said.
Thousands have been killed in the vast country - larger than France - although no accurate figures exist for a conflict that has remained largely under radar outside of Bangui.
"The plight of civilians in CAR... has gone from bad to worse," Bensouda said.
"The allegations include hundreds of killings, acts of rape and sexual slavery, destruction of property pillaging torture, forced displacement" and using child soldiers, she added.
"In many incidents, victims appear to have been deliberately targeted on religious grounds."
Reports by aid workers from several towns in the interior tell of attacks by armed bands, killing and looting, with nobody to prevent the violence.
The ICC prosecutor's investigation is not the first in Central Africa.
In 2007, former prosecutor Luis Moreno-Ocampo launched a probe into violence which lead to the arrest of former Congolese deputy president Jean-Pierre Bemba.
A former rebel leader, Bemba is currently on trial before the ICC for war crimes and crimes against humanity committed by his forces in 2002-2003 in a fight against Bozize's rebel movement in the CAR at the time.
Bensouda said the new initial probe, which is "unrelated" to the Bemba case, will determine whether there are grounds to open a full-blown probe in the troubled country.