|A boy plays among the ruins of a mosque in Bangui|
It said the abuse was alleged by around 10 children and reportedly took place at a centre for internally displaced people near the airport of the capital Bangui between December 2013 and June 2014.
A report in Britain's The Guardian newspaper said children as young as nine were involved, and that some were abused while searching desperately for food or money.
The regular sex abuse by peacekeeping personnel uncovered here and the United Nations' appalling disregard for victims are stomach-turning.
AIDS-Free World co-director Paula Donovan
France's defence ministry said prosecutors had "immediately" opened a case into the abuse after receiving the news last year, and that police investigators had travelled to the Central African Republic on August 1 to look into the case.
"The defence ministry has taken and will take the necessary measures to allow the truth to be found," it said in a statement.
"If the facts are proven, the strongest penalties will be imposed on those responsible for what would be an intolerable attack on soldiers' values."
Um, I think it was an attack on children by soldiers devoid of any moral values.
France sent troops to the Central African Republic in December 2013 as the country became engulfed in violence following a coup in March that toppled longtime leader Francois Bozize.
UN spokesman Farhan Haq confirmed that its rights investigators had conducted a probe last year following "serious allegations" of child abuse and sexual exploitation by French troops.
Aid worker suspended for leaking UN report
The internal report was commissioned by the UN Office of the High Commissioner for Human Rights (OHCHR) and passed on The Guardian via advocacy group Aids-Free World.
"The regular sex abuse by peacekeeping personnel uncovered here and the United Nations' appalling disregard for victims are stomach-turning, but the awful truth is that this isn't uncommon," Paula Donovan, co-director of Aids-Free World, told The Guardian.
That's for sure. It happened in Colombia, Japan, Afghanistan and Iraq, Papua New Guinea, and wherever military or paramilitary forces operate in foreign countries. Some soldiers seem to think they have a right to help themselves to the bodies of little children. There is probably some racism at work there. The UN and any other body responsible for sending these troops has to step up with a zero-tolerance policy, ZERO-tolerance! The guilty troops should be jailed and the soldiers country fined.
"The UN's instinctive response to sexual violence in its ranks — ignore, deny, cover up, dissemble — must be subjected to a truly independent commission of inquiry with total access."
The UN aid worker, Swedish national Anders Kompass, is based in Geneva and leaked the report to French authorities because his bosses had failed to take action, The Guardian reported.
He has been suspended and faces dismissal for breaching protocol, the paper said.
Mr Kompass is said to have passed on the confidential document before it was presented to senior OHCHR officials.
"This constitutes a serious breach of protocol, which, as is well known to all OHCHR officials, requires redaction of any information that could endanger victims, witnesses and investigators," UN spokesman Farhan Haq.
Since December 2013, violence has displaced nearly 900,000 people in the Central African Republic, including more than 460,000 who have become refugees — 10 per cent of the population.