PARIS — 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.