Japan's Ryota Murata beat champion Hassan N'Dam by technical knockout Sunday to capture the World Boxing Association middleweight title.

The 2012 Olympic champion avenged a controversial points loss to the Frenchman earlier this year with a convincing display in Tokyo, inflicting heavy punishment on N'Dam who failed to come out for round eight.

"I'm not crying," joked Murata after bursting into tears on seeing the referee wave the fight over, making him only Japan's second middleweight world champion -- and first in 22 years.

"I was surprised at the way the fight finished but I knew he was feeling the pace and wanted to finish the job quickly," added the 31-year-old, proudly cradling the WBA "regular" world belt.

"We were both pretty tired so it's a bit lucky he stopped. But there was no way I was going to lose that fight."

Gennady Golovkin remains the association's "super" champion and also holds the WBC, IBF and IBO titles.

"Boxing lovers will know there's a stronger middleweight champion than me out there," said Murata, referring to the unbeaten Kazakh. "I'll try my best to beat him."

Their last meeting in May ended acrimoniously after N'Dam won a split decision, even though Murata had largely dominated the fight and knocked his opponent down.

Two of the judges were suspended for six months while WBA president Gilberto Mendoza apologised to Murata, saying there were "no words to repair the damage".

N'Dam started the sharper of the two on Sunday as he looked to score early points.

The former WBO champion's gold gloves frequently found Murata's chin in the first two rounds.

But Murata wobbled the Cameroon-born champion with a right hook in the fourth, and another savage right in the sixth triggered sustained pressure which eventually took its toll on N'Dam.

Murata improved his professional record to 13 wins against one loss.

"After the first couple of rounds, I had no more strength left," said the 33-year-old N'Dam, who asked his trainer to untape his gloves after being caught with more stinging blows in the seventh round.

"I had nothing left in my arms, nothing in my legs."

N'Dam slipped to 36-3 with his defeat.

"I wanted to continue but my team decided that it wasn't worth taking more punches," he added.

"Murata put me under more pressure than last time and threw more punches. I congratulate him and hope we can fight a third time."