Police in India's technology hub of Bengaluru said on Wednesday they had begun investigating reports of a New Year's assault on a woman after a video emerged showing the attack by two men, as bystanders watched.
News of the video comes after a Reuters witness and media said several women revellers were groped and assaulted by a mob in the southern city in a separate incident reminiscent of last year's attacks in German cities blamed on migrants.
Police opened a case of molestation against two unidentified men, based on video images of the attack as the woman walked down a secluded lane in a residential area late at night, senior police official Ajay Hilori said.
"We have registered a first information report and started investigating," he told Reuters.
The closed-circuit video clip, whose authenticity Reuters could not independently verify, shows the driver of a scooter dismounting to grab the woman and drag her towards the vehicle, overcoming her efforts to get away.
The other man riding the scooter also briefly joins the skirmish, but the clip ends with the attacker throwing the woman to the ground before getting back on the vehicle to flee.
Some other people can be glimpsed at one end of the lane, but no one tries to intervene and stop the attack.
The woman in the clip, broadcast by several television channels, has not come forward to make a complaint, Hilori said.
Women in India are often reluctant to report such assaults for fear of being stigmatised by friends and relatives, although sex crimes are common, with more than 34,000 rapes reported in 2015, figures from the National Crime Record Bureau show.
Bengaluru, in the southern state of Karnataka, is home to many well-educated professionals.
It had widely been regarded as safer for women than New Delhi, which is often labelled the country's rape capital, for the many sex crimes reported there.
Authorities face criticism for not doing enough to stiffen a weak system of law enforcement and policing that leaves women vulnerable.
"These kind of things do happen," the state's home minister, G. Parameshwara, told the Times Now news channel after the Dec. 31 incident, in comments that appeared to blame the women for the assault, saying some of them dressed like Westerners.