Rescue workers get ready with their equipment after arriving Sunday in Tokyo's Akihabara district where a man with a knife ran over several people with a truck, then began stabbing them. (Itsuo Inouye/Associated Press)

A man who police said "was tired of life" drove into a crowd of pedestrians Sunday and then went on a stabbing rampage in Tokyo's premier electronics and video game district, killing seven people and wounding 10, authorities said.

The deadly lunchtime assault happened in Akihabara district after the attacker drove a rented two-tonne truck into a crowd, running over three people, public broadcaster NHK quoted an unidentified witness as saying.

News reports said the man jumped out of the truck and began stabbing the people he'd knocked down, then turned on horrified onlookers.

The attacker grunted and roared as he slashed and stabbed at his victims on a street crowded with Sunday shoppers, reports said.

"He was screaming as he was stabbing people at random," another unidentified witness told NHK.

Police confirmed seven deaths — six men and one woman — but they could not say whether the victims died from injuries from the truck or were stabbed to death.

Police said they arrested a 25-year-old man at the scene. "The suspect told police that he came to Akihabara to kill people," said Jiro Akaogi, a spokesman for the Tokyo Metropolitan Police Department.

"He said he was tired of life. He said he was sick of everything."

Local news reports initially said the man was a self-proclaimed gangster, but NHK later said the suspect was not a gang member.

At least 17 ambulances rushed to the scene, with TV footage showing rescue workers tending to victims in the street.

An unidentified witness told NHK the suspect dropped the knife after police threatened to shoot him. An amateur video filmed by a mobile phone showed police officers overpowering the bespectacled suspect.

Police earlier said 12 people were wounded but later lowered the number 10.

Akihabara district, known as Electric Town, is wildly popular with Japan's cyber-wise youth.

Once rare, stabbing attacks have become more frequent in Japan in recent years as violent crime has increased.

In one of the worst attacks, a man with a history of mental illness burst into an elementary school in Japan in 2001 and killed eight children. The killer was executed in 2004.