Controversial Swiss-born Islamic scholar Tariq Ramadan, a professor of contemporary Islamic studies at the University of Oxford, is being held by French police investigating accusations of rape.

A judicial source confirmed to Reuters that Ramadan was taken into custody on Wednesday. His detention comes in the wake of a preliminary investigation opened last year after two women filed police complaints against him, accusing him of rape.

The main complainant against Ramadan, the grandson of Muslim Brotherhood founder Hassan al-Banna, is former Salafist Henda Ayari, 40. She filed a complaint with French authorities in Rouen accusing Ramadan of sexually harassing her, raping her, and issuing death threats towards her.

The feminist activist also revealed that she had written about her experience in a book, but had been too fearful to print Ramadan’s name, L’Express reports.

At the time Ayari posted on her Facebook account about the situation, saying:

I have been silent for several years because of fear, because by threatening to press charges for the rape I was a victim of, he did not hesitate to threaten me and to tell me also that he could go after my children. I got scared and kept quiet all this time. I really hope that other women victims, like me, dare to speak, and denounce this perverted guru who uses religion to manipulate women!

The second complainant – a 42-year old convert to Islam – has alleged that she was raped by Ramadan in the Hilton hotel in Lyon in 2009.

Ramadan denies all accusations against him and maintains his innocence on all charges. He claims he is being targeted by “a campaign of slander clearly orchestrated by my longtime adversaries” and has filed a complaint for slander against Ayari.

The 55-year-old academic originally made his name as an author and commentator on modern Islam, as well as advising successive British governments on Islam and society.

Ramadan said in a statement in November, after he took a leave of absence from the University of Oxford, when the first charges were made public: “Contrary to reports in the French-language press, I have taken leave of absence upon mutual agreement with Oxford University, which will permit me to devote my energies to my defence while respecting students’ need for a calm academic environment.”

Ramadan was previously banned from entering the United States by the George W. Bush administration in 2004 after it was alleged he donated to the Association de Secours Palestinien (ASP/ Palestinian Relief Organisation) from 1998 to 2002. The U.S. government considered the ASP a group that funded terrorism by giving some of their donations to the anti-Israel terrorist organisation Hamas which is proscribed in the U.S.

Mr Ramadan’s U.S. travel ban was later lifted by then-Secretary of State Hillary Clinton during the Obama administration.