The U.N. secretary-general expressed shame Saturday over allegations that U.N. peacekeepers and foreign troops sexually abused children in Central African Republic.

"We are all deeply ashamed and horrified over the damage that has been done when peacekeepers exploit and abuse vulnerable people," Ban Ki-moon said at a summit for African leaders in the Ethiopian capital Addis Ababa. "The appalling acts of a few undermine the dedicated work of many. The U.N. has a zero tolerance policy on sexual abuse and exploitation. We must all work together to ensure accountability and transparency."

The U.N. human rights office said Friday that it had found six more cases of alleged sexual abuse against children by European troops in Central African Republic, including a 7-year-old girl who said she had to perform sexual acts on soldiers in exchange for water and cookies. A U.N. team recently interviewed five girls and a boy who claimed their abusers were part of French and European Union military operations in the troubled African country, the office of High Commissioner for Human Rights Zeid Raad al-Hussein said.

The sexual abuse allegedly took place in 2014 in or near a camp for displaced people near M'Poko airport in the Central African Republic capital Bangui, but only came to light in recent weeks, the latest in a string of similar allegations.

France, Central African Republic's former colonial ruler, deployed several thousand troops to the country in late 2013 as violence between Christians and Muslims sent thousands fleeing from their homes. An African Union mission that began in April 2014 was taken over by a U.N. peacekeeping force five months later, while the EU force ended an 11-month mission in March last year.

At a news conference in New York on Friday, the U.N. announced new allegations against U.N. peacekeepers.

Secretary-General Anthony Banbury came close to tears as he described four new child sex abuse cases in Central African Republic involving U.N. troops and police from Bangladesh, Congo, Niger and Senegal.

Banbury also announced an allegation of sexual assault against a minor by a member of Morocco's military contingent serving with the earlier AU mission.

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For all of 2015, Banbury said, there are likely to be 69 confirmed allegations of sexual abuse or exploitation in the U.N.'s 16 peacekeeping missions around the world.

The U.N. can report such allegations, but countries themselves are responsible for prosecuting their troops over such crimes.