Police have detained 20 men in central India's Madhya Pradesh state after a Swiss woman on a cycling trip was gang-raped.
No arrests have been made so far but police were questioning the men in connection with the rape and assault on the woman and her husband in the Datia district of the state, said senior police officer DK Arya.
He said the couple told police the woman had been raped by seven or eight men, but that it was dark and they could not be sure of the exact number. As a first step, police have registered a case of rape against seven unidentified men and are searching nearby villages, he said.
The attack comes three months after the fatal gang-rape of a woman aboard a New Delhi bus outraged Indians and spurred the government to pass laws to protect women.
The couple were on a three-month holiday in India. They had visited the temple town of Orchha and were planning to cycle to Agra to visit the Taj Mahal nearly 130 miles away.
They set out from Orchha on Friday and had pitched their tent in a forest near Jatia village when they were attacked by a group of men armed with wooden sticks.
The men beat up the husband, tied him to a tree and then raped the woman, police said.
The Swiss ambassador in India, Linus von Castelmur, has spoken to the couple and has demanded a swift probe of the incident.
Mr von Castelmur said he was "most distressed" by the incident and had assured the couple of all help and support. "Their health and treatment is the priority of the moment," the embassy said in a statement.
The embassy said it was in touch with local authorities in Madhya Pradesh and has urged a "swift investigation and for justice to be done".