Nonito Donaire became the new WBA world featherweight champion Saturday after defeating South Africa's Simpiwe Vetyeka in Macau in a fight that saw the Filipino boxing star take victory after an anti-climactic technical decision.

The bout was stopped after four rounds due to an "accidental headbutt" which left 31-year-old Donaire's left eye swollen and cut. According to the rules of the World Boxing Association, if such an incident happens after four rounds, the match goes to the scorecards.

A trio of judges scored 49-46 for Donaire.

The fight had started off slow, but Donaire floored his opponent in the second round with a right hook. Another left hook connected in the fourth round, knocking Vetyeka down again and sending the crowd wild.

But Donaire admitted he was disappointed with how the fight ended.

"It's disappointing that things ended the way it did and hopefully we can do it again, " he said at a press conference after the match.

"When I got headbutted I was really out of it, I didn't know what the hell was going on," he said.

"There was nothing else that I could do, I was at the biggest disadvantage," he said, adding that blood and medicine kept getting into his eye.

"I wanted to keep going but my dad kept saying: you're at a disadvantage, you're bleeding like crazy."

"The Filipino Flash" improved his record to 33-2 with 21 knockouts a match after he bounced back from a loss to Cuban Guillermo Rigondeaux in April 2013. He knocked out Armenian southpaw Vic Darchinyan in November of 2013.

He was working with his once-estranged father Nonito Snr, who was head trainer for the fight.

Vetyeka fell to 26-3 with 16 knockouts.

"I'm so disappointed about how the fight ended, and I don't know what to say, I am just disappointed," Vetyeka said at the press conference.

"The promoter is mentioning a match in November so that we can clear the air," he said.

"But for now I think it is proper for me to say congratulations to Nonito Donaire."