BANGUI, Central African Republic (AFP) - At least 22 people including three staff members of medical charity Medecins Sans Frontieres were killed during a weekend attack by gunmen on a Central African hospital, in the latest atrocity to hit the violence-plagued country.

   The brutal attack in the northwest was blamed on the mostly Muslim rebels known as the Seleka, whose coup in March last year unleashed a vicious cycle of sectarian violence.

   "Armed men from the ex-Seleka and of Fula ethnicity on Saturday afternoon attacked a hospital supported by MSF in the region of Nanga Boguila, killing at least 22 people, including three Central African employees of MSF and leaving a dozen wounded," an officer from the African-led MISCA peacekeeping force told AFP on Monday.

   MSF confirmed the death of its three employees, without giving further details.

   The gunmen had stormed into the building as local representatives and MSF employees held a meeting, the MISCA officer said.

   "The assailants first opened fire at a group of people, gunning down four of them. Then they went to the hospital where they killed 15 other people and three members of MSF.

   "They took computers and several other assets, breaking down doors probably in search for cash," added the officer.

   "France strongly condemns the deadly attack perpetrated on April 27 against the medical centre," said French foreign ministry spokesman Roman Nadal on Monday.

   "The perpetrators of this intolerable attack must be brought to justice,"

he said, while adding his praise for MSF's work "in difficult conditions and under threat to their lives".

   The Seleka rebels were ordered to disarm by their leader Michel Djotodia several months after they installed him in power in a coup. But some ignored orders and went on a killing, raping and pillaging rampage.

   Mostly Christian communities then formed "anti-balaka" vigilante forces to wreak revenge against Muslims, usually targeting innocent people.

   Djotodia resigned in January after failing to put down the violence that has claimed thousands of lives and displaced a quarter of the country's 4.6 million population. And today, extremists of the Seleka alliance actively encourage de facto partition.

   African and French peacekeepers, backed up recently by an EU force, have been struggling to curb the fighting ripping the country apart.

   "It is a region that is not completely secured, because our forces (are not large enough) to be deployed in other sites than the main cities like Bossangoa," said the MISCA officer, referring to a city about 100 kilometres from the scene of the MSF attack.

   The weekend attack came as 1,300 Muslims left the capital Bangui on Sunday under heavy guard.

   Tens of thousands have already fled northwards, almost emptying the south of the country of Muslims. They have travelled to predominantly Muslim areas in the north, while thousands of others have fled across borders into Chad and Cameroon.

   The religious and ethnic faultlines that are driving the conflict are particularly disheartening in a country where these groups lived peacefully alongside each other for generations despite a succession of coups, misrule, army mutinies and strikes.

   Earlier in April, UN chief Ban Ki-moon made an impassioned plea on the warring parties to prevent a new genocide on the continent, 20 years after Rwanda.

   A 12,000-strong UN force is scheduled to deploy in September in the former French colony, taking over from 2,000 French and 6,000 African Union soldiers already in place.