About a million people in the Central African Republic - 20% of the population - have fled their homes during months of communal violence after Seleka rebels seized power last March.
In recent weeks there have been more reports of atrocities committed by rival militias in an atmosphere of increasing insecurity.
Peter Bouckaert, director of emergencies for Human Rights Watch, told the BBC's Focus on Africa programme he saw French peacekeepers do nothing while corpses were mutilated at the airport at the capital Bangui on Wednesday. The French defence ministry has not commented.
Some readers may find his testimony disturbing.
It was an absolutely horrific scene when we arrived at the entrance to the airport in Bangui.
We found a large mob of people, and French soldiers at the scene. The crowd was mutilating two bodies of Muslim men that they had just killed with machetes.
There were probably about a dozen people involved in the mutilation. They were probably members of the anti-balaka Christian militia.
Large crowds of people had gathered, including children.
They cut one man's genitals off and put them in his mouth.
It really was a scene of absolute horror.
People were filming this on their cell phones and many were laughing. When we left the scene, they said: "Keep on filming, because we're not yet done."
No safe area
The French soldiers were there, just sitting metres away, and didn't stop this horrific mutilation from taking place.
The soldiers were heavily armed, they could have easily parked one of their armoured cars next to these two bodies, which were about 50m [164 ft] apart, and stood by them until the Red Cross came to collect them.
But instead they checked out the scene and then they got back in their cars and drove away.
There is no more safe part of the city for Muslims. We see them being killed everywhere in Bangui, and Christians as well.
We were at the morgue two days ago, and it really was a scene out of Dante's Inferno. They showed us the death records in case after case of people who had been lynched in the street, shot, burned.
These scenes are repeating themselves throughout the country, not just in Bangui.
The Christian population has suffered tremendous abuses under the Seleka for the last 10 months.
Now the Seleka is leaving, and every position they leave, the Muslim community is attacked, entire Muslim communities are just being wiped off the map.
I met the head of military intelligence for the Seleka, he said it was over for Seleka. We saw him drive out of Bangui the next day in a large convoy of Seleka generals, heading for Chad and protected by Chadian peacekeeping troops.
They're not only escaping the slaughter but also escaping justice for the crimes they committed against the population.
It is the Muslim community which is facing the wrath of the majority Christian population for the crimes committed by the Seleka.
We're talking about children being slaughtered in front of their Muslim parents with machetes.
It really is an orgy of bloodshed.