A man suspected of killing seven people by ramming a truck into a crowd and then stabbing passersby in Tokyo detailed his plans in a series of text messages sent from his cellphone to a website, police said Monday.

Two men offer prayer for victims of Sunday's knifing rampage in Tokyo's Akihabara district. (Katsumi Kasahara/Associated Press)Tomohiro Kato, 25, of Shizuoka, a prefecture west of Tokyo, admitted posting messages to an online bulletin board warning of his rampage up to seven hours before arriving in Akihabara district, they said.

Kato is accused of ramming a crowd of pedestrians with a two-tonne truck and then stabbing 17 bystanders in the popular video game and electronics district.

Investigators say he told them that he decided to stage the attack two or three days earlier and chose the Akihabara area because he had visited it and knew "many people gather there."

In one of the earlier messages titled "I will kill people in Akihabara," the poster said he plans to crash a vehicle into a crowd and "when I can't use the car anymore, I will use a knife," police quote Kato as writing, according to the Asahi Shimbun newspaper.

"Goodbye, everyone," the message ends.

Police are still trying to match transmission records to confirm whether Kato indeed sent the messages.

The text messages continued as the suspect made his way to the capital from Shizuoka prefecture east to the capital, first boarding a train then renting a two-tonne truck, police say.

Worked for auto company: reports

Police investigators examine the crime scene in Tokyo's Akihabara district Sunday afternoon. (Itsuo Inouye/Associated Press)Kato lived in the city of Susono and was a temporary worker at an automaker, Japanese media reported.

At 6:31 a.m., a message is posted: "It's time. I'm leaving," the Asahi Shimbun reports.

About an hour later, the writer expresses concerns that "strong rain" could ruin "perfect preparations." Shortly after, another message says: "Oh well. Even if at a smaller scale, rain or shine, I go."

At 11:45 a.m. a message announces the sender's arrival in Akihabara. About 20 minutes before the attack, the last message declares, "It's time."

Investigators are still trying to determine the motives of the suspect, though according to police, Kato told him he had "gotten sick of the world."

Japanese taken aback by crime

The rampage shocked the country, which is known for its low crime rate compared to other industrialized nations. With a population of 12.7 million, Tokyo is considered safe thanks to tight restrictions on guns.

The scene of the attack, the intersection of Chuo and Kanda Myojin streets near the JR Akihabara station, was covered with flowers and other offerings on Monday.

"Everyone says that Japan is a safe country, but I'm not sure if that's true anymore," said Sayaka Itoda, a young woman who had come to leave flowers.

Government officials were scrambling to respond to the attack, holding an emergency meeting on Sunday to discuss ways to secure crowded public spaces. One idea was to limit access to large knives such as the 23-centimetre one used in the attack.

"Obviously, the suspect possessed the knife without a legitimate reason," said Nobutaka Machimura, the chief cabinet secretary. "I think we have to seriously consider what we can do to step up the restrictions."

Gun violence is rare in Japan compared to stabbings. In March, one person was stabbed to death and at least seven others injured when a man attacked passersby with two knives outside a shopping mall in Ibaraki prefecture in eastern Japan.

In January, a 16-year-old boy attacked five people on a shopping street in Tokyo's Shinagawa ward.

The Akihabara attack also happened on the seventh anniversary of a knife attack in an elementary school near Osaka ended in the death of eight children. The attacker, who had a history of mental illness, was executed in 2004.

With files from the Associated Press