Tariq Ramadan, a prominent Swiss-born scholar of Islam, was charged in France with rape on Friday, based on accusations made against him four months ago by two women. He has denied the accusations as a smear.
Mr. Ramadan, a 55-year-old theologian and philosopher, was placed under formal investigation on charges of rape and rape of a vulnerable person, according to a spokesman for the French judiciary.
The spokesman, who spoke on condition of anonymity in line with department policy, said that Mr. Ramadan would be kept in custody while a judge decides on whether to grant him bail. The prosecution has requested that he remain under arrest.
Mr. Ramadan is the author of several books on Islam and on the Western world, and is considered by some experts to offer a moderate, tolerant version of the faith. But critics, especially in France, say he is a demagogue who hides radical views behind a polished media persona.
The women's accusations have put a dent in his projected image as a pious family man. He has characterized them as part of an organized campaign of slander by his enemies.
Mr. Ramadan was taken into custody for questioning on Wednesday, when he answered a police summons in Paris. Now that a formal investigation has begun, Mr. Ramadan's fate remains uncertain.
In France, complex criminal cases are handled by special magistrates with broad investigative powers. Defendants placed under formal investigation will not automatically go to trial, as the magistrates can drop cases they believe show insufficient evidence.
If Mr. Ramadan goes to trial and if he is convicted, he faces up to 15 years in prison on the charge of rape, and up to 20 years on the separate charge of rape of a vulnerable person. That charge was included because Mr. Ramadan's second accuser is partly disabled, requiring her to walk with a crutch because of a car accident.
Mr. Ramadan was first accused in October, in the aftermath of the Harvey Weinstein sexual abuse scandal, which led many Frenchwomen to report personal experiences of harassment or assault.
Henda Ayari, a French author and activist, accused Mr. Ramadan in a Facebook post that month of having sexually assaulted her in a Paris hotel room in 2012. On the day she published the Facebook post, she filed a police complaint in her hometown, Rouen, in northern France.
Ms. Ayari had already written about the assault in a 2016 book on how she had been drawn to Salafism, a radical Islamist movement, before breaking away from the ideology. But she had not identified the attacker as Mr. Ramadan.
The second accuser, who has not been identified publicly, filed a complaint against Mr. Ramadan shortly after, accusing him of having raped and assaulted her in a hotel room in the central French city of Lyon in 2009.
The woman, a 45-year-old convert to Islam, told French newspapers that she had corresponded with Mr. Ramadan on Facebook and met him in his hotel on the sidelines of a conference to discuss religion. When she went to his room, she said, she was raped and beaten.
Both women said Mr. Ramadan had threatened them into silence.
Mr. Ramadan is a grandson of Hassan al-Banna, who founded the Muslim Brotherhood in Egypt in the 1920s.