TOKYO - A JAPANESE man who admitted murdering a former top bureaucrat has said he planned to attack as many as 10 people because of the death of his dog, officials said on Tuesday.

'I hear the man made a (target) list of 10 people including former welfare bureaucrats and pensions officials over his dog,' said Health, Labour and Welfare Minister Yoichi Masuzoe.

'I cannot understand why he committed such a rash crime,' he said.

Japanese police arrested Takeshi Koizumi, 46, on Sunday after he turned himself in to police with a knife covered with blood and claimed responsibility for attacks last week targeting former bureaucrats.

'I was going to kill more,' Koizumi told police, the Japanese news agency Jiji Press reported. 'I was going to attack 10 people, including former vice ministers and their wives.' A 66-year-old former vice welfare minister and his wife were killed last week at their home in Saitama, north of Tokyo, while the wife of a 76-year-old former vice welfare minister was stabbed on her doorstep.

Police have confirmed only that Koizumi admitted murdering the official, although he has also admitting attacking the two wives, according to local media.

Both former officials once served as directors at the welfare ministry's troubled pensions division, sparking speculation that the attacks might be linked to the loss of millions of pension payment records.

But Koizumi told police that he bore a grudge over the death of his pet dog, which was put down at a health centre more than 30 years ago, saying he 'had thought of taking revenge once becoming an adult", Jiji said.

Police have confirmed that the blood on the knife matched those of the victims, public broadcaster NHK said. A police spokesman said he was unable to confirm the report. -- AFP