Tokyo  - Police on Wednesday arrested a 21-year-old Japanese man on suspicion of obstructing public service after he wrote messages on a mobile phone bulletin board warning that he would commit a similar crime to the Akihabara stabbing rampage.

"I will commit a crime like the Akihabara stabbing at noon. I already bought knives and guns. There will be news about my crime tomorrow," Takuya Nomura wrote on June
12.

A user of the mobile phone site reported the message to police, which led to Nomura's arrest on Wednesday in central Ibaragi province.

Nomura admitted to sending the messages and told the police he was frustrated. He carried no guns or knives.

The Akihabara stabbing shocked Japan on June 8, when Tomohiro Kato killed seven people in a rampage and injured 10.

According to the Metropolitan Police Department, Kato, 25, intended to kill passersby on the streets of Tokyo's famous electronics town as he drove a two-ton truck at more than 40 kilometres per hour. He hit three people and stabbed them as well as shoppers and passersby.

Kato had posted messages on a mobile phone site to warn of his intended actions. He was tired of life, the car-factory worker had written, and was angry with his company for dismissing temporary dispatch workers. Though he was a temporary worker, Kato was not to be dismissed.

"I am not trying to defend Kato, but it's not hard to imagine he felt desperate. Workers at plants are treated like machines. If your human dignity is not respected, it would be difficult to respect others' dignity," Takeshi Koyano of Japan Construction and Transport Industry Workers Solidarity Union said Wednesday.

Dispatch workers are often dismissed without any insurance or help in finding another job, he said.

The group fears that the Akihabara crime would trigger discrimination against temporary dispatch workers, especially in the manufacturing sector. (dpa)