TOKYO--Japanese mobile telephone content providers are setting up safeguards to protect young people amid shock after a disgruntled young man used his phone to document his plans for a stabbing rampage.

An association representing the mobile content industry announced this week a list of 22 criteria that would allow online sites to use a label showing that they are suitable for minors.

Nearly all Japanese mobile telephones allow access to the Internet, where special sites designed for the small screens have become an increasingly lucrative business.

"We want to support the upbringing of young people by giving them the means to use new technology in complete safety," said a joint statement outlining the new label.

Mobile phone websites that want the safety label would have to agree to abide by 22 criteria including that they will closely monitor postings and report suspicious messages to authorities.

Mobile content providers have been alarmed by bad publicity as a number of people use websites to arrange group suicides or announce plans for crimes.

Last month, troubled 25-year-old auto worker Tomohiro Kato posted dozens of messages warning of plans for a massacre as he drove a rented two-tonne truck to Tokyo.

He killed seven people and injured 10 more by swerving his truck into a crowded pedestrian area and then bursting out and stabbing people at random.

Authorities came under fire after the crime for failing to spot his warnings.

Kato, who also posted hundreds of messages earlier detailing his loneliness, told police that he grew even more agitated as he was ignored in the virtual world.

The government said after the massacre that it would research new technology to filter messages on the Internet.