NEW DELHI (AFP) - A screaming woman locked in a van sparks scant reaction from passers-by in a social experiment in New Delhi, as India once again faces up to a series of gruesome rapes and murders.

Experts and activists said the video posted on YouTube pointed to a general apathy in India about violence against women despite outrage in some quarters over the gang-rape and lynching of two girls in the country's north.

"There's still an apathy about what's happening to women, an insensitivity on the issue, although attitudes are changing," said women's activist Ranjana Kumari.

The video, which has been viewed more than 1.2 million times since it was posted last week, shows a white van parked in a secluded area of Delhi with the windows blacked out at night. Although the screams of a woman are clearly heard coming from inside, a handful of men are seen walking and cycling past. Some stop to listen before calmly moving on.

Finally, a young man tries to break into the van, clearly upset about the "staged rape" occurring inside. An elderly man is also seen attacking the van with his stick.

The video was posted by a group called "YesNoMaybe" in what they said was a social experiment in the wake of the horrific attacks on the two girls, aged 12 and 14, late last month in Uttar Pradesh state.

The attacks reignited anger over violence against women with small-scale protests held in the state capital and in Delhi, while a political row erupted over a perceived lack of law and order in Uttar Pradesh.

Since then, the media has highlighted a string of alleged rapes and hangings of women in Uttar Pradesh, the country's most populous state.

The attacks came just 18 months after the fatal gang-rape of a student on a bus in Delhi, a case that made global headlines and left India reeling over its treatment of women.

The video sparked an outcry online, with some saying they were "ashamed", while others said the lack of help was probably reflective of attitudes in most capital cities.

The group that posted the video did not draw any conclusions.

"We hear about rapes every day in India, which leads to widespread protest," the group said in a message accompanying the video.

"Thousands of people attend candlelight marches but only a handful of people act when it really matters.

"So we set out to find how many people would actually help if someone's in trouble."

Ms Kumari told AFP that many were reluctant to intervene, fearful of being dragged into a lengthy police investigation or even face charge themselves in India's notoriously inefficient criminal justice system.

"There is also still this rationale that the woman must have done something to deserve the attack. There must be some justification for what is happening to her," said Ms Kumari, director of the Delhi-based Centre for Social Research.

Social scientist Shiv Visvanathan said he was wary of drawing conclusions from the video but he said many Delhi residents were scared of being attacked themselves if they intervened.

Professor Visvanathan, a professor at the Jindal Global University just outside Delhi, said the capital drew millions of young men from impoverished and remote rural areas searching for work.

As a result, he told AFP: "There's an absence of a community spirit in many parts of Delhi, a feeling that we should work together to stop these attacks happening.

"It's a city of strangers."