Paris prosecutors are investigating accusations that French soldiers in the Central African Republic sexually abused children they were sent to protect.
The French probe follows an initial United Nations investigation into the allegations a year ago - both of which were kept secret until a report in the Guardian newspaper forced officials to publicly acknowledge them.
A UN worker leaked information about the UN investigation to French authorities last year, the UN Secretary-General's office said in a statement. That worker, identified by the Swedish government as Swede Anders Kompass, has been suspended and is now under internal investigation.
The Central African Republic has seen unprecedented violence between Christians and Muslims since late 2013. At least 5,000 people have been killed, and about one million are displaced internally or have fled the country. France sent troops in late 2013 and the UN set up a 12,000-strong peacekeeping force in September last year.
Early in 2014, the Office of the High Commissioner for Human Rights in the country's capital, Bangui, carried out an investigation after "serious allegations of sexual exploitation and abuse of children by French military personnel", the UN Secretary-General's office said today.
The UN investigation has now been passed on to French authorities, said a spokesman for the UN human rights office in Geneva, Rupert Colville. The French government was informed of the accusations in July 2014, the Defence Ministry said in a statement.
About 10 Central African children told UN officials in the Central African Republic that they were sexually assaulted by French soldiers around the M'Poko airport between December 2013 and June 2014, the statement said.
The allegations of sexual abuse, the secretive nature of the probe and the treatment of the suspended UN worker all cast a new shadow on the world body, which has faced accusations of abuses by its peacekeeping forces in the past.
The UN high commissioner for human rights, Zeid Raad al-Hussein, was the author of a lengthy report on preventing sexual exploitation by peacekeepers that the global body commissioned a decade ago after a scandal involving UN troops in Congo.
Known as the Zeid Report, it recommended among other things that allegations of abuse be followed by a professional investigation and that UN member states should pledge to prosecute their soldiers as if the crime had been committed in their own country.
The allegations are also damning for France, which sees itself as a model of human rights, and has thousands of troops around former colonies in Africa sent to protect civilian populations in conflict zones.
French President Francois Hollande and UN Secretary-General Ban Ki-moon met in Paris tonight but refused to take questions from reporters afterwards and did not say anything about the alleged abuse in a brief public statement.
The Paris prosecutor's office has opened a preliminary investigation and authorities went to the Central African Republic in August to begin investigating.
If the accusations are proven true, the French Defence Ministry said it would ensure "the strictest sanctions against those responsible for what would be an intolerable attack on the values of a soldier".
The UN Secretary-General's office said the leak of the internal documents did not constitute "whistleblowing" but was a "serious breach of protocol".
"Any issue of sex abuse is a serious issue," the deputy spokesman for the UN Secretary-General, Farhan Haq, told reporters in New York. "At the same time, there are concerns we have about the protection of witnesses and victims."
Sweden's government said it was "worrisome" if Kompass was suspended for sharing information about sexual abuse of children on an international mission.
"We are not entirely sure what Kompass is accused of or why he has been suspended," Anders Ronquist, legal chief of Sweden's Foreign Ministry, said in a statement. "The UN must have zero tolerance toward sexual abuse of children and ensure that suspicions of such abuse are investigated."