Australia's Jeff Horn has defeated champion Manny Pacquiao for the WBO world welterweight title in a controversial decision that stunned the boxing world.

The 29-year-old former schoolteacher improved his record to 17-0-1 after the three judges unanimously scored the fight 117-111, 115-113 and 115-113 in his favour, but many across Twitter felt like they were watching a different fight.

Pacquiao, despite his slower start, dominated much of the later stages and even caused the referee to tell Horn to "show me something" in the ninth round or the fight would be stopped.

However the Filipino was unable to capitalise on his dominance and knock Horn out, who made it to the end of the bloody 12-round encounter still showing signs of aggression.

When the final scorecards came through, among those to criticise the decision included former heavyweight world champion and Olympic gold medallist Lennox Lewis and boxing trainer and commentator Teddy Atlas.

"This is what's wrong with boxing," Lewis wrote via Twitter. "Horn was very game but I'm hard pressed to see how he could have won that fight by any stretch!"

Speaking ringside after the fight, Atlas said: "They gave a trophy, a win, a huge win to Horn – the local kid – for trying hard.

"You're not supposed to get it for trying hard. You're supposed to get it for winning and I thought Pacquiao won the fight.

"If you go by the real rules, the Marquess of Queensberry rules, who lands the cleaner punches?"

Despite the loss, Pacquiao said he respected the decision and said he would "absolutely" return for the contracted rematch.

"Very tough. I didn't expect that tough," he told Reuters reporters. "It's okay, it's part of the game. That's the decision of the judges, I respect that."

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