The stabbing of 20-year-old female idol Mayu Tomita has sparked a discussion over the effectiveness of the anti-stalking law, which some experts say should include a clear statement on preventing the kind of online stalking the latest victim was facing.

The current anti-stalking law "cannot directly crack down on stalking on social networking websites" as it is not worded to include harassment via social media, Yohei Shimizu, a Tokyo lawyer well-versed in online defamation cases, said Monday.

According to media reports, 27-year-old Tomohiro Iwazaki, who was arrested Saturday for stabbing Tomita nearly two dozen times in the neck and chest, had apparently repeatedly sent messages to her Twitter account.