One of Japan’s most prominent bloggers has been stabbed to death minutes after giving a seminar on how to resolve personal disputes on the internet.

Media reports said Kenichiro Okamoto, better known by his blogger name Hagex, died on Sunday evening after reportedly being attacked by a man he had argued with online.

The suspect, Hidemitsu Matsumoto, allegedly followed Okamoto into the toilets after he had ended his talk at a venue in the south-western city of Fukuoka.

Okamoto was stabbed several times before staggering out of the toilets after his assailant, who fled on a bicycle, according to the Mainichi Shimbun newspaper.

Okamoto, who sustained stab wounds to the chest and neck, was taken to hospital where he was confirmed dead. His attacker reportedly handed himself in almost three hours after the attack.

Moments before the fatal stabbing, the 41-year-old had shared advice at a public event on how to deal with online disputes.

According to reports, the suspect had posted messages containing personal abuse directed at Okamoto and other commenters on the blog. The Mainichi quoted a source as saying that Okamoto “had got into trouble before with internet users over the content of the blog”.

In a message purportedly written immediately after the stabbing, Matsumoto said he had continued to abuse Okamoto by opening a new account every time his existing account was deleted.

He added: “I am going to go now to my neighborhood police box to voluntarily surrender and take responsibility for my actions.”

Matsumoto, 42, reportedly confessed to stabbing Okamoto, telling police he had grown to “hate” the celebrity blogger and wanted to kill him.

Regarded as a leading expert on cybercrime and the dark web, Okamoto worked for an IT security consulting firm and made regular TV appearances.

Japanese Twitter users paid tribute to the blogger, with many voicing disbelief over the violent nature of his death. “Rest in peace, Hagex,” one user wrote.

The IT journalist Daisuke Tsuda said he was shocked to learn of Okamoto’s death. “How could this have happened?” he wrote.

Online personalities and journalists are often victims of online abuse in Japan, where attempts are being made to crack down on hate speech.