Violence has erupted in the Indian state of Madhya Pradesh after a banned two-finger test (TFT) was carried out on an alleged rape victim.

The 16-year-old, who was found unconscious 780 km east of Madhya Pradesh's capital Bhopal, was allegedly raped by a passenger of a bus, with the aid of three other men. She was then abandoned on the outskirts of the town.

The girl was later taken to Shyam Shah Medical College, where she was subjected to the controversial test.

When doctors concluded that there was no evidence of recent sexual intercourse, students from the Hostel for Scheduled Castes and Tribes asked to speak with the victim. As police denied them permission, students retaliated by throwing stones at the officers.

The four suspects were arrested and taken into custody. They alleged the girl fabricated the rape story after falling down from the running bus, as the driver refused to take her to her stop.

"Action will be taken against those found guilty. Investigations are on," Inspector General Pawan Srivastava told the Times of India. "I have also ordered an inquiry into how a banned test was done despite guidelines against the same."

The TFT, or virginity test, allows doctors to inspect the hymen of women to verify rape claims. It is also supposed to test vaginal laxity and decide whether the victim frequently has sexual intercourse.

The test, considered unscientific and a violation of the victim's privacy, was banned in India last March.

Under new guidelines decided by Indian health ministry, victims must now be supplied with fresh clothing and must be treated sensitively. Doctors and other medical staff will have to attend sensitivity training classes.

The ministry has told hospitals to set up adequate rooms for forensic and medical examinations of victims.

No third person may be present in the room unless the doctor is male, in which case a female can also attend.