Numerous cases of rape have been reported in India sparking widespread outrage. Reuters

Five villagers detained in connection with the gang-rape of a 39-year-old Swiss woman in the central Indian state of Madhya Pradesh have admitted to the crime, according to local police.

The tourist was on a cycling tour with her husband when they were attacked by a group of men who are said to come from the Datia region, 200 miles south of New Delhi.

"We have detained five men and they have confessed to gang-raping the woman and attacking her husband," local police official MS Dhodee told AFP.

"They [suspects] were passing by, noticed the couple putting up their tent and saw an opportunity to attack and rape the woman," he added.

The detainees will face charges after the completion of formalities. A massive operation has been launched to track down other suspects.

Although the police have detained 20 people, the exact number of perpetrators is still not clear as it was dark when the crime took place; the number of assailants is put at seven or eight.

Sources investigating the case have told the Indian daily The Hindu that the victim was brutally raped. The assailants "tied up the man and gang-raped the woman in his presence," senior police official D K Arya told the newspaper.

The couple, who were on a three-month tour of India, were reportedly planning to visit the Taj Mahal in Agra.

The victim has since left for New Delhi to receive medical attention, the Press Trust of India reports, quoting Inspector General (Chambal Range), SM Afzal.

Meanwhile, a "distressed" Swiss embassy in India has called for a "swift" probe into the incident.

"The embassy is most distressed with the gang-rape of a Swiss national in Madhya Pradesh. The ambassador has been able to speak to the victim and her partner and has assured them of all possible support. Their health and treatment is the priority of the moment. The embassy has also been in touch with the local authorities and has requested swift investigation and for justice to be done," said a Swiss embassy statement.