A Japanese man wrongly convicted of murder who was the world's longest-serving death row inmate has been awarded $1.4 million in compensation, an official said Tuesday.

The payout represents 12,500 yen ($83) for each day of the more than four decades that Iwao Hakamada spent in detention, most of it on death row when each day could have been his last.

The former boxer, now 89, was exonerated last year of a 1966 quadruple murder after a tireless campaign by his sister and others.

The Shizuoka District Court, in a decision dated Monday, said that "the claimant shall be granted 217,362,500 yen," a court spokesman told AFP.

The same court ruled in September that Hakamada was not guilty in a retrial and that police had tampered with evidence.

Hakamada had suffered "inhumane interrogations meant to force a statement (confession)" that he later withdrew, the court said at the time.

The final amount is a record for compensation of this kind, local media said.

But Hakamada's legal team has said the money falls short of the pain he suffered.

Decades of detention -- with the threat of execution constantly looming -- took a major toll on Hakamada's mental health, his lawyers have said, describing him as "living in a world of fantasy".

Hakamada was the fifth death row inmate granted a retrial in Japan's post-war history. All four previous cases also resulted in exonerations.