NEW : Head of U.N. refugee agency ' deeply distressed ' Amnesty International says peacekeepers have failed to prevent ethnic cleansing . Antonio Guterres , head of the U.N. refugee agency , said he has `` witnessed in the Central African Republic a humanitarian catastrophe of unspeakable proportions . The UN has been accused by human rights groups and the United States of failing to protect civilians in eastern Congo from a wave of violence that began last year when rebels seized control of Goma. Christian and Muslim militia groups are warring in the Central African Republic .
NEW : Head of U.N. refugee agency ' deeply distressed ' Amnesty International says peacekeepers have failed to prevent ethnic cleansing . The UN has been accused by human rights groups and the United States of failing to protect civilians in eastern Congo from a wave of violence that began last year when rebels seized control of Goma. Christian and Muslim militia groups are warring in the Central African Republic .