Tokyo: Japanese police arrested four people for allegedly threatening copycat killings online after a man posted similar messages on websites before stabbing seven people to death, officials said Tuesday.

"I'm sick of it all. I'm going to do it too," a jobless 29-year-old wrote on the hugely popular 2-Channel website. "I'm going to kill 100 people in Ikebukuro," he said, referring to a popular Tokyo shopping district, a Tokyo Metropolitan Police official said.

The suspect allegedly posted the message a day after the June 8 stabbing attack in another Tokyo district, in which a man rammed pedestrians with a truck, jumped out and knifed more than a dozen people. Seven people died and another 10 were injured.


Tomohiro Kato, who was arrested on the scene splattered with blood, foretold the attack in hundreds of messages on the internet.

Similar messages have shown up repeatedly in the days since that massacre.

In Hiroshima, police arrested a 19-year-old man Sunday over a message allegedly posted on June 9 saying, "That incident in Akihabara ... I will kill everyone" at a popular local shopping street, police spokesman Hideo Yamamoto said.

In northern Yamagata, a 29-year-old man was arrested on Thursday for allegedly posting a message saying he planned to run over people with his truck. At Chubu International Airport in central Japan, a 24-year-old man was detained after allegedly vowing in a message to "stab people" at a nearby train station on Monday, officials said.

A junior high school student was also questioned in northern Niigata after allegedly posting a note saying he would burn down a train station on June 30 and then "randomly commit murders."