An anti-groping device aimed at tackling sexual harassment on public transport has sold out within an hour after being launched in Japan this week.

Key points: Women in crowded trains and other public places in Japan often face sexual harrassment and groping

Women in crowded trains and other public places in Japan often face sexual harrassment and groping The stamp also contains a black light, which is used to identify the assailant

The stamp also contains a black light, which is used to identify the assailant The company, Shachihata, says the stamp is a "small step" towards tackling the problem

The stamp is designed to be carried in a handbag or pocket and allows victims to mark their assailants, known as 'chikan' with an invisible ink stamp in the shape of a hand.

People can then use the device's black light to identify those who have been marked.

Despite the country's relatively low violent crime rate, women in crowded trains and other public places in Japan often face sexual harassment and groping, are blamed if they speak up about it and the crime often goes unreported.

Shachihata, the stationery and stamp company that developed the device, flagged a trial of it in May after footage of two teenage girls chasing an alleged groper down a train station platform in Tokyo was shared widely on social media.

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A spokesman told the Japan Times that a limited trial run of 500 sets of the product, known officially as a "nuisance act prevention stamp", sold out in less than an hour after going on sale on Tuesday (local time).

The stamp, which retails for 2,700 yen ($38), includes a retractable cord and a black light for revealing the stamp.

In a statement on Twitter, the company said it was a "small step" towards tackling the problem and the company would continue to work on other ways to "contribute to society in the future".

"The most ideal would be a world free of sexual crimes and violence, including molesting," the statement said.

"However, this is too big a challenge, and it is a difficult social problem to encourage recognition and change of everyone by the action of one person alone."

The anti-groping device is designed to be carried in a bag or pocket. ( Supplied: Shachihata )

Other measures used to try and discourage gropers include badges for schoolgirls to wear on backpacks warning gropers to stay away and that any crime would be reported, as well as women-only carriages.

A smartphone app developed by the Japanese police allows women to press a "repel groper" icon, which produces a written message saying "There is a groper here. Please help".

The app also releases sound saying "Please stop".