Barrios, 30, held onto his belt despite being dominated for several rounds by 46-year-old Filipino icon Pacquiao, returning to the ring for the first time after a four-year retirement.

Barrios was awarded the fight 115-113 by one judge, with the other two cards scoring it 114-114.

The result drew a subdued reaction from the MGM Grand Garden Arena crowd, who had roared on Pacquiao as he attempted to make a spectacular return to boxing.

At times, it seemed as if Pacquiao was poised to write another improbable chapter in his 30-year professional career as he used all of his guile and experience to frustrate Barrios.

But Barrios rallied furiously over the final three rounds -- he was deemed the winner of those rounds on all three cards -- to do just enough to force a result that sees him retain his title.

"I thought I won the fight," Pacquiao said afterwards. "I mean, it was a close fight. My opponent was very tough. But it was a wonderful fight.

"I was trying to find a way to finish the fight but my opponent was so tough. He threw punches in combination and with defense, so it was hard."

Barrios, meanwhile, felt he had done enough to deserve the draw.

"I thought I pulled it out," Barrios said. "But I still tip my hat to Manny. It was an honor to share the ring with him, somebody with so much experience who has accomplished so much in this sport. We left everything in the ring, nothing but love and respect."

Barrios admitted he had been awed by Pacquiao's remarkable reserves of energy and stamina.

"That's crazy -- his stamina, he can still crack and he's still strong as hell. His timing, his rhythm, everything. He was still a very awkward fighter to figure out."