Russia's Evgeny Tishchenko won the Olympic heavyweight boxing gold medal to a chorus of boos from the crowd after beating Kazakhstan's Vasily Levit on a unanimous points decision.
Levit, whose world champion opponent required medical attention for a cut in the third and final round, had to settle for silver despite seeming to land more punches and steer the fight.
The bronze medals went to losing semi-finalists Rustam Tulaganov of Uzbekistan and Erislandy Savon of Cuba.
The majority of the audience, in a Riocentro arena that was barely half full, reacted to the score announcement with derision while a pocket of Russian fans waved flags and celebrated.
There were more boos during the medal ceremony, although Levit gestured for silence by putting a finger to his lips.
The judges scorecards had Levit narrowly ahead after the first round, with two out three giving it to him, but they were unanimous in giving the second to the Russian.
Levit, who prevented the world champion from using his height and longer reach to any effect by smothering him, steered the Russian repeatedly on to the ropes and came on strong in an often scrappy third round.
Both men hit out wildly, with Tishchenko slipping on the canvas and momentarily losing his balance as they grappled.
The referee called a halt with 51 seconds remaining for inspection of a cut, more common now that Olympic boxers no longer wear headguards, before the fight resumed and ended in a flurry of punches.
Russian athletes have been regularly booed in Rio as a result of the country's doping scandal that has overshadowed the Games, but Tishchenko faced plenty of questions about the scoring.
To his increasing irritation, he was asked whether he considered himself a worthy winner and whether he agreed with the outcome.
"If the judges gave me the medal, they had reasons for it," he said, speaking through a translator.
"For sure I am really upset about this (booing) because I respect my opponents and all the crowd," he added. "I just cannot understand why they booed in such an outrageous way."
Levit, who put his silver medal in his pocket as he left the arena after the award ceremony rather than keeping it around his neck, refused to criticise anyone and told reporters his opponent deserved a better reception.
"There is a solidarity between fighters and I think that every boxer that comes to the ring deserves respect," said the Kazakh.
"In my head I was thinking that I won and the coaches were quite happy with me and told me I did everything they asked me to do for the fight. But you see how it ended up."