Japanese boxer Naoya Inoue retained his undisputed super bantamweight world title with a unanimous decision victory over compatriot Junto Nakatani after a gripping 12-round contest in Tokyo on Saturday.

The 33-year-old, famously known as 'The Monster', extended his winning streak in world title bouts to 28 as judges scored the fight 116-112, 115-113 and 116-112 in his favour.

Both boxers entered the bout unbeaten at 32-0 in a contest which was billed as the biggest boxing match in Japanese history after Nakatani moved up a division late last year.

Inoue charged early before Nakatani appeared to close the gap in the latter half of the fight as the pace intensified, but a clash of heads late in the 10th round opened a cut above the challenger's eye and stalled his momentum.

"Today I executed the plan that I'd been saying before the fight, to stay focused on winning, to make sure I was the one who came out as the winner," Inoue said.

"As you all know, Nakatani is a mentally strong boxer. The fact that he is in the (top 10) pound-for-pound rankings makes this win worthwhile."

The win improved Inoue's overall record to 33 victories, with 27 knockouts.

(Reporting by Suramya Kaushik in Bengaluru; Editing by Lincoln Feast.)