The attackers "tied up the man and raped the woman in his presence", local police official S.M. Afzal said, adding that they stole 10,000 rupees (HK$1,400) and a mobile phone from the woman.

The couple were on their way to Agra, home of the Taj Mahal monument in northern India, when they stopped to camp for the night in a village.

Indian media reports said the men were wielding sticks when they attacked the couple.

The rape victim, aged about 40, was admitted to hospital in Gwalior city, 342 kilometres from the state capital Bhopal.

She was conscious yesterday and speaking to authorities, police said. Officers were said to be questioning 13 men in connection with the attack.

Concern remains high in India over the safety and status of women and girls in the country of 1.2 billion.

The attack comes just months after thousands of women took to the streets to protest against India's treatment of women following the fatal gang-rape of a 23-year-old student on a bus in New Delhi in December.

Last Monday, Ram Singh, one of six accused on trial over the December assault, was found hanged in his high-security jail cell in New Delhi.

Police suspect he hanged himself, but his family says he was murdered.

In 2003, a 36-year-old woman Swiss diplomat was abducted in the car park of a popular New Delhi auditorium, driven away by two men and raped.

She was freed later nearby. No one was convicted for that attack.

Rape is one aspect of a wide range of violence, including domestic assaults, against women in India that claims many thousands of lives each year, according to rights workers.