An association comprising major social media service operators Wednesday urged its member firms to ban users' solicitation of suicide through their sites following the alleged serial murder case near Tokyo in which the suspect contacted Twitter users expressing suicidal thoughts.

The association, formed in July this year to improve internet safety for children and young people, is led by CyberAgent Inc., DeNA Co., Facebook Japan, Gree Inc., LINE Corp. and mixi Inc.

The association is urging member firms to limit access to their services by users who offer to help people commit suicide in their posts and to cooperate with police more closely when they find particularly alarming posts.

In the murders in Zama just outside Tokyo earlier this year, Twitter was the key communication tool that brought together the suspect and some of the nine victims. The suspect used a Twitter account to boast knowledge about hanging to get in touch with people who wanted to commit suicide.