(Bangui, CAF) - Burundian and Chadian troops in the African force deployed in the Central African Republic (CAR) have exchanged fire in Bangui, raising new questions Tuesday about the stance of the Chadian contingent of a UN-mandated force sent to tame a country rocked by sectarian killings.

The Burundian military reported the exchange occurred on Monday as the Chadians, mainly because they are Muslim, face accusations of complicity with the Seleka rebels who overthrew president Francois Bozize in March in the predominantly Christian country now gearing up for Christmas.

Lieutenant-Colonel Pontien Hakizimana, head of the Burundian contingent in the African force MISCA, told AFP in Bujumbura that his men were disarming former rebels when Chadian troops from MISCA threw a grenade and opened fire on them, prompting some Burundian elements to return fire, wounding three Chadians.

"On Monday morning we intercepted six armed ex-Seleka and we disarmed them," Hakizimana told AFP from Bangui.

A group of Chadian soldiers went by on a truck and threw a grenade at the Burundians, which exploded without causing any casualties, he said.

"Then the Chadians left with the ex-Seleka, firing in all directions," he said, adding some of his men came under fire and retaliated, wounding three Chadians.

"The Chadians soldiers came back in greater numbers in the afternoon and attacked our positions," Hakizimana said, adding that Burundian troops repelled them without a problem.

"The soldiers from the Burundian contingent are very disciplined and battle-tested and have nothing to do with yesterday's incidents," Hakizimana. "We have no dispute with any part of the Central African population."

There was no immediate comment from the Chadian contingent.

A military source in Bujumbura said relations between the Burundians and the Chadians had been strained ever since the Chadians in the MISCA had been re-deployed outside the capital and the Burundians tasked with securing Bangui.

The rare incident in which peacekeepers traded fire put fresh pressure on the Chadian contingent, which accounts for 850 of the 3,700-strong MISCA force but is accused by many people in Bangui of backing the Seleka.

It follows an incident on Monday when Chadian soldiers opened fire on hundreds of stone-throwing protesters, mostly Christians, killing one man and wounding around 40 others, three seriously.

Traditionally influential in the Central African Republic, President Idriss Deby Itno's Chad is France's main partner in its efforts to re-establish peace in the country.

But the growing defiance of Central Africans toward the Chadian contingent is complicating the task of the 1,600 French troops deployed to the country since the beginning of December.

The deployment came after interim President Michel Djotodia officially disbanded Seleka, but some of its members went rogue, leading to months of killing, rape and pillaging -- and prompting Christians to form vigilante groups in response.

Amnesty International says some 1,000 people have been killed since December 5, mostly by Muslim ex-rebels but also in Christian reprisal attacks.

Chadian and Sudanese mercenaries within Seleka are blamed for many of the worst crimes against civilians.

After a brief respite, violence has returned to the capital where communal tensions remain high and the situation volatile.

'No to France!'

French soldiers meanwhile are being accused by Muslims of siding with the country's Christian population as they disarm the Seleka and leave the Muslim population defenceless against many Christians who seek revenge for Seleka excesses.

Overnight Monday, gunfire erupted in the mainly-Muslim PK5 neighbourhood where two Muslims had been lynched earlier and their bodies mutilated.

Residents said Tuesday that the attack was carried out by Christian militias while several hundred protesters gathered to denounce what they perceived as the inaction of French troops.

"The French took the side of those who are attacking us," one of the protesters, Jibril Assil, said. "They give weapons to the anti-balaka (militias)."

In the neighbourhood, signs hung from homes saying: "No to France."

Shouting French President Francois "Hollande is a criminal," the protesters marched to the doors of the presidency in the centre of the city which was guarded by French troops. The group dispersed calmly shortly afterwards.

In the runup to Christmas Eve, activity was relatively normal in the capital as some stores broadcast Christmas songs from loudspeakers and salesmen offered red Santa Claus hats at dusty crossroads under a baking heat.

Because of a night curfew, churches will hold Christmas Eve mass in the afternoon.