Light heavyweight Michel Borges had most in the 9,000-seat arena firmly on his side from the moment he stepped in to the ring and the judges made him the winner on unanimous points, to roars of approval and dancing in the stands.

But Cameroon's Hassan Ndam Njikam one of three professional boxers competing in the Olympics for the first time in its long history wagged his finger in the air and shook his head in disbelief and was later seen remonstrating with boxing officials.

As part of moves to boost its popularity, especially in the United States, Olympic boxing has allowed in the pros, dropped headguards for men and ditched the punch-counting method to decide fights.

But if the AIBA, the governing body, hoped it would result in fewer controversies it may have to think again – Njikam, 32, said he felt he won at least two of the rounds and some observers agreed.

"I told them that I came from far away for this competition and I am professional," he said, asked by AFP what he had been saying animatedly to boxing officials just outside the venue, as his family looked on.

"I took too much time to enter the fight in the first round because I wanted to know what he was going to do.

"But the second and third rounds I put on the pressure and I think I hit him with more punches than he hit me with so I'm very unhappy with the decision, but this is boxing."

Very proud

The first professional boxer in 112 years of Olympic boxing, earlier in the day, had no such trouble.

Italy's Carmine Tommasone, who came into his lightweight bout with a perfect 15-0 record, simply had too much speed, power and guile for Mexico's Lindolfo Delgado and was deservedly awarded a unanimous points decision by the judges at ringside.

The Italian hurt the taller Mexican, 21, in round two with a clumping overhand right that had Delgado smiling and urging the Italian to bring it on begrudging recognition that the punch hurt.

Tommasone continued to bamboozle Delgado in the third and final round, hitting the Mexican around with combinations that Delgado had no reply to.

"I am very proud," Tommasone said of being the first boxing pro at an Olympics.

"I was asked by my federation to come to the Olympics and I was very happy to do so -- for me, it's the most important competition in the world."

Britain and the United States the two American fighters were roundly booed by the mostly Brazilian crowd sent an ominous warning of intent as they emerged unscathed through five bouts between them to underline their status as favourites in Rio.

Team USA's men's team is under pressure to deliver medals in Rio after failing to even get on the podium in London four years ago a humiliating fall from grace for the most successful country in Games boxing history.

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