France has charged the ex-wife of a top Islamic State official with crimes against humanity on suspicion of enslaving a teenage Yazidi girl in Syria, French media reported.

A woman identified as Sonia M., the former wife of the jihadist group's head of external operations Abdelnasser Benyoucef, was charged on March 14, Le Parisien said Saturday.

The Yazidi woman, who was 16 when she was forced into slavery by Benyoucef, accused Sonia M. of raping her twice and knowing that her husband was raping her, the report said.

The woman, now 25, said she was held for more than a month in 2015 in Syria, where she was not allowed to eat, drink or shower without Sonia M.'s permission.

Sonia M. denied the allegations against her in a March 14 interview with French investigators, saying "only one rape" had been committed by her former husband.

The teenager "left her room freely, ate what she wanted, went to the toilet when she needed to", she said in her interview, seen by AFP.

Sonia M.'s lawyer Nabil Boudi slammed the charges as "opportunistic accusations", saying that prosecutors were seeking "to make her responsible for the most serious crimes, because the courts have not managed to apprehend the real perpetrators".

An arrest warrant has been issued for Benyoucef, according to a source close to the investigation.

France launched an investigation in 2016 into genocide, crimes against humanity and war crimes committed against ethnic and religious minorities in Iraq and Syria since 2012.

The probe has focused on crimes suffered by members of the Yazidi and Christian communities as well as members of the Sheitat tribe, according to France's PNAT anti-terror unit.

"The aim is to document these crimes and identify the French perpetrators who belong to the Islamic State organisation," PNAT told AFP.