Five men have been arrested over the alleged gang-rape and extortion of a Japanese tourist held as a sex slave for nearly a month in a basement near a famous Buddhist shrine in India, officials said on Sunday.

The 22-year-old's ordeal began in Kolkata, the capital of West Bengal state, where she was befriended by three local men shortly after arriving on Nov 20, one of the city's top police officers said.

The men, one of whom spoke Japanese, first managed to persuade her to withdraw around $1,200 in cash before traveling with her to the holy shrine of Bodh Gaya in the neighboring state of Bihar.