* Mainly Muslim Seleka rebels losing ground
* Muslim civilians threatened by Christian militias
* Senior U.N. official urges more support for peacekeepers
By Emmanuel Braun
BANGUI, Jan 27 (Reuters) - Central African Republic's Muslim minority faces a rising wave of reprisal attacks and foreign governments must do more to prevent the country being torn apart, the top U.N. human rights official said on Monday.
Almost one million people, or a quarter of the population, have been displaced by fighting since the mainly Muslim Seleka rebel movement seized power in the majority Christian country last March, unleashing a wave of killing and looting.
Christian self-defence groups, known as "anti-balaka" or anti-machete, have taken up arms against them and the United Nations estimates that more than 2,000 people have been killed in the resulting bloodshed over the past 10 months.
Seleka leaders are now abandoning the capital Bangui with their remaining fighters, raising the risk of reprisal killings targeting Muslim civilians.
"The security and human rights situation has further deteriorated over the past few days," U.N. High Commissioner for Human Rights Navi Pillay said in a statement.
"Muslim civilians are now extremely vulnerable. Many are being pushed out of the country, alongside ex-Seleka, and are now fleeing, mostly towards the Chadian border," she said.
Looting and mob violence mainly targeting predominantly Muslim neighbourhoods of Bangui have intensified in the past week despite the presence of a French intervention force and thousands of African peacekeepers.
"We simply cannot let the social fabric of this country be torn apart," the U.N.'s Pillay said. "I call as a matter of utmost urgency upon the international community to strengthen peacekeeping efforts... Many lives are at stake."
Most Muslim civilians have now fled Bangui or are preparing to do so. A Reuters witness in the Miskine neighbourhood watched on Monday as looters dismantled Muslim-owned shops and homes, most of which had already been stripped of their goods and furniture during previous waves of theft.
Gunfire erupted as French forces, firing tear gas, tried to disperse angry Christian crowds attempting to erect barricades on the streets. The witness saw one woman with a gunshot wound.
"As Seleka loses ground, Muslim communities are being systematically attacked by anti-balaka. There's killing on a daily basis," Peter Bouckaert, emergencies director for Human Rights Watch, told Reuters.
The country's new interim president Catherine Samba-Panza, who was sworn in last Thursday, has already called for more international troops to help quell the violence.
A 1,600-strong French force and another 5,000 African troops are already deployed in Central African Republic.
The European Union last week pledged around 500 additional soldiers, but it was unclear which countries would contribute troops and when they would arrive.
The Catholic Archbishop of Bangui, Dieudonné Nzapalainga, and the head of the country's Islamic community, Imam Oumar Kobine Layama, during a visit to Britain, urged London to back the EU force and plans for a larger U.N. peacekeeping mission.
"We believe that only a strong U.N. force can deal adequately with the growing instability and provide the framework for sustainable political and reconciliation processes in our country in the long term," the two religious leaders said in a letter to British Prime Minister David Cameron. (Additional reporting by Tom Miles in Geneva and Michael Collett-White in London; Additional reporting and writing by Joe Bavier; Editing by Gareth Jones)