The 56-year old scholar is presently under detention in France.

He is there since February, after being charged with a separate rape case.

The alleged Switzerland incident took place in a Geneva hotel in 2008.

The Tribune de Geneve newspaper quoted justice ministry spokesman Henri Della Casa as saying that a case has been formally opened against the Oxford University professor.

"I confirm the opening of an inquiry," Della Casa was quoted as saying by the daily.

The victim and accuser lodged her complaint in April this year.

AFP news agency quoted the accuser's lawyer, Romain Jordan, as saying that it was prudent move.

"The prosecutors and Geneva police have worked quickly and worked well," Jordan said, adding that the decision was a major advance that "demonstrates the seriousness of the allegations made by our client."

Swiss authorities will now travel to France to her Ramadan's side of the story.

He, however, has pleaded not guilty in the French rape charges.

Meanwhile, a French court has cleared him of a third rape allegation by a Muslim woman, who accused him of raping her nine times between 2013 and 2014.

Ramadan is a Swiss citizen. His grandfather was the founder of Egypt's Muslim Brotherhood movement.

Image: Irfan kottaparamban/Wikipedia