All mobile phones sold in India from January 2017 must have a panic button enabling the user to call for help, the government has said, amid concern for women's safety after a series of violent crimes in recent years.
From January 2018, mobile phones must also have a built-in global positioning system (GPS), the ministry of communications and technology said in a statement.
"Technology is solely meant to make human life better and what better (use) than for the security of women," said the statement, released late on Monday.
Keeping a finger pressed on number 5 or 9 on the new mobile phones should trigger an emergency call, the ministry said. With smartphones, an emergency call must be triggered when the power button is pressed three times in quick succession, it said. It did not give further details.
Some politicians and police officials have called for women to take self-defence training, to "dress decently" and not to loiter after dark, provoking protests from women's rights activists.
Online retailers including Flipkart, Amazon India and Snapdeal are selling products they say are aimed at women's safety. These include pepper spray, batons, brass knuckles and lipstick stun guns ranging in price from about 200 rupees ($3) to almost 7,000 rupees.
India is the world's second-biggest market for mobile phones, with more than 1 billion users.