France is investigating allegations of child abuse in Central African Republic by soldiers that it sent there to stem an outbreak of sectarian killing, officials said on Wednesday.

The alleged abuse took place between December 2013 and June 2014 at a centre for displaced people at M’Poko airport in the capital Bangui, and concerned about 10 children, France's Defence Ministry said.

"A preliminary investigation by the Paris prosecutor has been open since July 31, 2014," a Justice Ministry spokesman said. "The investigation is ongoing." A Defence Ministry source said no suspects had yet been identified.

France intervened in Central Africa, a former French colony, some 18 months ago to stem violence between Christian militias and largely Muslim Seleka rebels who had seized power. It started withdrawing some of its 2,000 troops this year, handing over to U.N. peacekeepers.

The allegations are acutely embarrassing for a country that prides itself on its ability to despatch rapid intervention forces, notably as a way of maintaining stability and French influence in its former African colonies. 

Britain's Guardian newspaper said it had acquired a U.N. report that first raised allegations of the rape of young boys by French troops.

A French judicial source said the prosecutor's office had received that report in July 2014, and had asked for assistance from Central African authorities in investigating whether there had been abuse of minors.

A spokesman for U.N. Secretary General Ban Ki-moon confirmed that the U.N. Office of Human Rights in Bangui had conducted a human rights investigation in the late spring of 2014.

It said the probe followed serious allegations of sexual exploitation and abuse of children by French military personnel, before the establishment of a U.N. peacekeeping mission.

It said the unedited version of the internal report had been leaked to French authorities in late July, even before it had been passed to senior U.N. officials, and that a Geneva-based U.N. official had been suspended for a "serious breach of protocol".

France's defence and foreign ministries issued a joint statement saying that "all necessary measures" would be take to establish the truth, and that "the toughest sanctions" would be applied to anyone proven to be guilty of abuse.