More than 20 people have been killed in India in the last two months, according to media reports, after rumours were spread on smartphones about child kidnappers, thieves and sexual predators.

The attacks -- usually targeting outsiders -- have left authorities scrambling to mount an effective response, with awareness campaigns and public alerts having limited effect.

A stern statement issued by the electronics and IT ministry late on Tuesday expressed the government's "deep disapproval" to the senior management of WhatsApp over the "irresponsible and explosive messages".

"The government has also conveyed in no uncertain terms that WhatsApp must take immediate action to end this menace," it added.

In a letter to the Indian government, WhatsApp said it "cares deeply about people's safety" and had taken steps to combat the scourge of fake news and hoaxes.

"We're horrified by these terrible acts of violence and wanted to respond quickly to the very important issues you have raised," WhatsApp said in the letter seen by AFP.

The company said it was working with Indian researchers to better understand the problem and had introduced changes it said would reduce the spread of unwanted messages.

It would also soon launch a new label in India to help users identify messages that had been forwarded as opposed to written by someone they know.

Rumours on WhatsApp about child kidnappers saw eight men killed in eastern Indian last year but the same information has since resurfaced.

Attacks have been reported in at least 11 states recently, most recently in Maharashtra where five men were bludgeoned to death by a crazed mob on Sunday.

Last week a "rumour buster" official tasked with warning the public against such hoaxes was killed in northeastern Tripura.

With more than 200 million users, India is WhatsApp's biggest market. Its parent company Facebook has also been grappling with a global data privacy scandal.

WhatsApp said it planned to run a public safety campaign in India "given its importance" to the company, and mentioned efforts by police to use its platform to raise awareness about its misuse.

"We believe that false news, misinformation and the spread of hoaxes are issues best tackled collectively: by government, civil society and technology companies working together," WhatsApp said.

"With the right action we can help improve everyone's safety."