Virginia Raggi on Monday tweeted her solidarity with the woman, who was raped near Rome's main train station last weekend.
Police arrested a suspect, identified as a 22-year-old from India's Bengal region. Police said the man offered the woman a ride as she was waiting for a taxi, before leading her to an isolated street where he threatened to kill her, then raped her. A nearby resident heard the woman's screams and alerted police.
Police in Florence are investigating allegations that two paramilitary policemen raped two American women. A Polish woman was gang raped last month at an Italian beach resort.