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Video - Diaz snatches welterweight title
Felix Diaz won the Dominican Republic's first Olympic boxing gold thanks to a one-sided light-welterweight victory over title holder Manus Boonjumnong.
The pair were level at 2-2 after two rounds but Diaz dominated round three, connecting with a flurry of shots to take a decisive 10-3 lead.
Thailand's Boonjumnong could not recover and Diaz ended up winning 12-4.
Somjit Jongjohor did win gold for Thailand, beating Cuba's Andry Laffita 8-2 in the flyweight final.
The 33-year-old Somjit, the world championship silver medallist, showed greater accuracy and led throughout the bout to secure victory.
Laffita, the Pan-American champion, never gave up but struggled to find his range and to hit an elusive target.
Somjit's victory will make up for the disappointment of Athens in 2004 when he lost to eventual champion Yuriokis Gamboa of Cuba despite taking a three-point lead into the final round.
"I wanted to win for the Thai people who have been supporting me for the past four years," he said.
"I went through so much. It hurt so much but I kept trying. I'm sure today people in the south of Thailand will be very happy."
Diaz, meanwhile, was delighted with how he performed in Beijing, saying: "I wanted to come and win a medal, any kind of medal and I got the gold.
"I made history because I'm the second boxer in the history of the Dominican Republic to win a medal.
"This is so important for me but also for my country. I don't have a coach, I have a magician.
"I want to dedicate my victory to my parents, my two little kids and to all the people in the Dominican Republic who have been watching my bouts at three in the morning every day just to support me."