UN Secretary-General Ban Ki-moon has warned that French and African soldiers in Central African Republic were "overwhelmed" by a "state of anarchy," a day after Chadian troops began withdrawing from the peacekeeping mission.
During a brief visit to the country on Saturday, Ban appealed for more help and said the international community was at risk of repeating the mistakes of the 1994 Rwanda genocide where some 800,000 died.
"I commend the African Union and French forces for making a difference," he said in a speech before the interim government. "But they are under-resourced and overwhelmed by the sheer scale of the need."
"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 called for "the immediate deployment of more troops and police".
The UN Security Council is due to approve next week a 12,000-strong UN peacekeeping force for the former French colony, which will take over authority from African Union troops in an attempt to restore order to the impoverished country.
But that force is not expected to arrive until September, stoking fears of a security vacuum, as the interim government struggles to control intercommunal violence that has killed more than 2,000 people since December.
Two thousand French peacekeepers and 6,000 African Union forces have failed to stop a conflict that erupted after the mostly Muslim Seleka rebels seized power a year ago in the majority Christian state.
Christian militias, known as anti-balaka, sprung up to protect the population after Seleka took to looting and killing but now stand accused of human rights abuses themselves and last month were branded as "terrorists" by the African Union.
A long-promised European Union force is expected to start deploying at the end of this month, adding 800 new troops.
A UN report on Friday accused Chad of killing 30 civilians and wounding 300 in a crowded market, although Chad denied the allegation, saying troops were ambushed by anti-balaka.
The US ambassador to the United Nations, Samantha Power, plans to visit the country next week.