BANGUI -- U.N. Secretary-General Ban Ki-moon vowed Saturday that the world would not forget Central African Republic, as he visited the country wracked by sectarian violence that has left thousands dead and forced most of the nation's Muslims to flee.

Ban's visit -- his first since the bloodshed erupted in December -- came just before he goes on to Rwanda to mark the 20th anniversary of the genocide there. The U.N. chief has been among the most vocal of world leaders in calling on countries to prevent a similar tragedy in Central African Republic.

"The international community failed the people of Rwanda 20 years ago. And we are at risk of not doing enough for the people of the CAR today," Ban told members of a transitional council tasked with preparing the country for elections by February 2015.

"Atrocity crimes are being committed in this country," he said. "Ethno-religious cleansing is a reality. Most members of the Muslim minority have fled."

International aid groups have criticized the U.N. response to the crisis, though Ban himself has spoken forcefully about the need to protect civilians in Central African Republic, where at one point earlier this year Muslims were being killed by Christian mobs in the streets on a near-daily basis.

"There is a hole in the heart of Africa," Ban said Saturday. "Every day, I wake up thinking about your trials and troubles. Everywhere, I have called on leaders to step up their efforts," he said. "Some say this is a forgotten crisis. I am here to help make sure the world does not forget."

Ban ventured well beyond the security of Bangui's airport, meeting interim President Catherine Samba-Panza and even visiting Muslims at one of the last remaining operational mosques in the capital. Displaced families who have spent weeks sleeping outdoors on the grounds of the mosque held signs reading "Ban Ki-moon: We want to go to the north."

Forces from neighbouring Chad, a predominantly Muslim country, have helped to evacuate tens of thousands of Muslims fleeing the violence in Central African Republic but the U.N. estimates some 19,000 Muslims remained trapped in places too dangerous to leave them there.

African countries have contributed 6,000 peacekeepers to the effort in Central African Republic, though neighbouring Chad began withdrawing its 850 troops on Friday amid a dispute over clashes last weekend that left more than 30 civilians dead. The Chadian forces maintain they were returning fire, while a U.N. preliminary investigation has found they shot indiscriminately into a crowd of civilians.

France has 2,000 troops in its former colony, though a European Union effort to send reinforcements has stalled amid an apparent reluctance to contribute forces.

The U.N. Security Council will vote on a U.N. peacekeeping force in April. Ban has urged council members to act quickly on his recommendation for a 12,000-member peacekeeping mission.

"The world agreed on our collective responsibility to protect a population when the state is unwilling or unable to do that basic job," Ban said Saturday. "The people of CAR should not have to run and die while the world decides whether to keep its promise. You have waited long enough."