Thousands of Muslims tried to flee the capital of the Central African Republic (CAR) on Friday, only for their mass convoy of cars and trucks to be turned back as crowds of angry Christians taunted: "We're going to kill you all."

The drama unfolded as Amnesty International said it had uncovered evidence of a fresh massacre in a village where the sole surviving Muslim was an orphaned girl aged about 11, and France said it would send an extra 400 peacekeeping troops.

Some cars were crammed with as many as 10 people as the convoy made its way through Bangui, the second such attempt to escape in a week, the Associated Press reported. Christians gathered along the road to shout abuse and threats.

The convoy was turned back because African peacekeepers feared it would come under attack in some volatile parts of Bangui. The desperate procession was halted in the Miskine neighbourhood, where one vehicle tumbled into a ditch on the side of the road.

On the orders of a Burundian captain, the peacekeepers went from vehicle to vehicle instructing everyone to return to a local mosque, according to an AP journalist at the scene.

Lieutenant Rosana Nsengimana, of the African peacekeeping force known as Misca, said: "The convoy escorted by Burundian forces returned to its departure point because of a problem in a neighbourhood on the north end of the city where the Muslims would have had to pass through."

The neighbourhood in question witnessed fresh fighting on Friday with at least one person killed in a grenade attack by Christian militiamen, according to witnesses at a nearby mosque. French peacekeepers had to rescue two other severely injured people from an baying crowd that had set tyres on fire and was shouting anti-Muslim and anti-French slogans.

Muslims have increasingly been targeted by Christians who took up arms against a mostly Muslim rebel group known as the Seleka, which seized power in a coup a year ago, committing scores of atrocities along the way. The Christian militias, known as the anti-balaka, seem intent on what they perceive as vengeance.

Amnesty has warned that a campaign of ethnic cleansing is causing a Muslim exodus. On Friday Donatella Rovera, a senior crisis adviser at Amnesty, described the scene at a village in the north-west of the country.

"We saw bodies littering the streets," she said. "Several of them had been partially burned. Others had been partly eaten by dogs and other animals. One was the body of a little baby who could not have been more than seven or eight months old. We saw more than 20 bodies but we think that there were several more.

She continued: "All the houses of the Muslim population had been burned or looted and in one of the houses I found a little girl of about 11. She was the only Muslim survivor of the village: the others had either fled or been killed. She was crouching in a corner. She had been hiding there since the day of the massacre. She had not eaten or drunk anything. She was terrified and could not stand at all.

"She said that her father had been killed and her mother had been killed. She was not speaking very much. There had not been any peacekeepers there at all even though this place was a place that had already seen confrontation between anti-balaka and Seleka forces earlier."

The anti-balaka have stepped up their attacks in recent weeks, forcing tens of thousands of Muslims to flee for their lives. Most head to neighbouring Chad, which is predominantly Muslim.

There have been almost daily killings of those who could not escape, their bodies mutilated and dragged through the streets despite the presence of peacekeepers.

Muslims made up about 15% of the CAR's 4.6 million population before the present crisis. Now entire neighbourhoods of Bangui are empty. Only one mosque remains in the town of Yaloke, where previously there had been eight, according to Human Rights Watch. "The anti-balaka militias are increasingly organised and using language that suggests their intent is to eliminate Muslim residents," HRW said this week.

Medecins Sans Frontieres said 1,000 people – mostly Muslim – were in danger in the south-west town of Carnot. "Armed men have announced that they intend to track down and kill all the city's Muslims," it said. "Anyone who hides Muslims is also at risk."

Catherine Samba-Panza, the country's first female leader and a Christian who hopes to reach across the sectarian divide, vowed this week that her administration was "going to go to war against the anti-balaka". She said: "The anti-balaka have lost their sense of mission. They are now the ones who kill, who pillage, who are violent."

But on Thursday Richard Bejouane, the self-proclaimed leader of the militias, warned her not to intervene. "Declaring war on the anti-balaka amounts to declaring war on the Central African population," he told hundreds of militiamen gathered in Bangui. Bejouane claims their ranks number 52,000, including 12,000 in the capital.

International peacekeepers deployed in the country have failed to halt the violence. France said it would send an additional 400 troops to join its existing 1,600-strong force.