A Japanese hacker who hijacked computers in order to issue death threats, leading to the arrest of several innocent people, was jailed on Wednesday after a game of cat and mouse with police.

Yusuke Katayama, 32, used computers to make a series of threats in 2012, including that he would kill people at a comic book event, attack an airplane and target a kindergarten attended by the grandchildren of Emperor Akihito.

"He committed the crime, and the purpose of it was for police to make wrongful arrests," said Katsunori Ohno, presiding judge at Tokyo District Court, adding that Katayama's actions had been "vicious".

Katayama used a virus to gain control of strangers' computers through which he issued threats and a series of riddles that captured the attention of the national media.

The National Police Agency had to apologize after it emerged that officers had extracted "confessions" from four people they arrested, even though they had nothing to do with the threats.

Police held one of the suspects for several weeks before media received anonymous messages containing information that investigators conceded could only have been known by the real culprit.

The messages said that details of the computer virus had been strapped to a cat in Tokyo. Then the police found the cat and tracked down Katayama.