* U.N. accuses Chadian troops of killing 30 in market attack
* Chad says they were responding to militia ambush
* Residents in Bangui rejoice as Chadian troops depart (Releads with Chad troop withdrawal, adds comments from Chad, MISCA, residents)
By Jean-Frederic Perriere
BANGUI, April 4 (Reuters) - Chad began withdrawing its troops from Central African Republic's peacekeeping mission on Friday as a U.N. report accused its soldiers of killing 30 civilians and wounding 300 in an attack on a crowded market last week.
Chad's Foreign Minister Moussa Faki Mahamat denied the allegation, saying the troops had been ambushed by Christian "anti-balaka" militia and had responded.
A series of violent incidents involving Chadian troops has stoked fury in the former French colony, culminating in Chad's decision on Thursday to withdraw its troops from the African Union peacekeeping force, known as MISCA.
The decision was met with joy in the streets of the capital Bangui on Friday, although the government said in a statement it regretted their withdrawal.
"Chadian officers under MISCA command and around 200 soldiers have left in the direction of Chad," Hassan Sylla, Chad's communications minister, said.
Chad, the Central African region's dominant military power, had around 850 soldiers serving in the peacekeeping force.
Sylla said the first troops left aboard a convoy of a dozen military trucks, escorted to the edge of Bangui by MISCA peacekeepers. French TV news channel France 24 broadcast images of a military plane that had arrived at Bangui's airport to help repatriate the troops.
Chadian forces were also preparing to leave the towns of Bossangoa, Kaga Bandoro, Batangafo, Ndele, Bouca and Kabo, Human Rights Watch researcher Peter Bouckaert said on Twitter, raising fears the power vacuum could leave Muslims vulnerable in the inter-communal violence that has killed thousands.
Chad's troops have been accused of siding with the mainly Muslim Seleka rebels whose seizure of power last year led to tit-for-tat violence with Christian militia.
The U.N. human rights office carried out a preliminary investigation, interviewing survivors in hospital and visiting the scene of the March 29 attack. Spokesman Rupert Colville said a convoy of pick-up trucks from Chad's regular army entered the market in the capital's PK12 district and started firing.
"It allegedly opened fire on the population without any provocation. As people fled in all directions in panic, the soldiers continued to fire indiscriminately," he said.
While Chadian troops participate in the African Union force deployed in Central African Republic, the soldiers were not part of the peacekeeping contingent, the investigation found.
"At the time of the shooting the market was full of people, including many young women and girls buying and selling produce," Colville told a news briefing in Geneva.
Speaking on Radio France Internationale, Chad's Foreign Minister blamed the shooting on Christian militia he said had ambushed the Chadian troops. "Naturally they responded and that provoked an outcry," he said.
MISCA General Jean-Marie Michel Mokoko also told France 24 the Chadian soldiers acted after being targeted by anti-balaka.
Civil society groups had collected 240,000 signatures for a petition seeking the withdrawal of the Chadian troops.
"It's exactly what we asked for. The charges against Chadian forces in MISCA are well founded. This is a cause for joy," said Gervais Lakosso, who helped organise the petition.
"It seems too good to be true," said a manager at a stationery shop in the capital.
The withdrawal is seen as a blow for France, which has deployed 2,000 troops in a bid to restore peace to its former colony, a landlocked nation rich in gold, diamonds and uranium that has seen little but instability since independence in 1960.
A new interim civilian government took over from Seleka in January but has struggled to contain the violence.
"We've made very clear and the (U.N.) Secretary General has made very clear that there is a desperate need for a good size peacekeeping force," said Colville. "He has requested 10,000 troops in all. We're nowhere near that number at this point."
A long-promised European force of 800 troops tasked with securing Bangui's airport and improving security in the capital is due to start deploying by the end of the month.
French military spokesman Gilles Jaron said on Friday the new force would be made up of 450 French troops, bringing the total number of French soldiers in the country to 2,450. (Additional reporting by Tom Miles and Stephanie Nebehay in Geneva, Marine Pennetier in Paris and Madjiasra Nako in N'Djamena; Writing by Emma Farge and Joe Bavier; Editing by Janet Lawrence)