Brazil won their first Olympic gold medal of Rio 2016 here today as judoka Rafaela Silva overcame huge pressure to triumph in the under 57 kilograms category in front of a crescendo of chanting, singing and raucous celebrations.

The 24-year-old had required a golden point period to reach the final before a sole waza-ari proved enough to overcome Mongolia's Sumiya Dorjsuren.

Her performances throughout the day were exactly what was needed the spark the Arena here into life, as well as the Games itself, particularly as she is a local girl and holds a rags to riches story line worthy of a Hollywood movie.

Born in the notorious City of God favela community in the West Zone of the host city, Silva took up sport - first football and then judo - principally as a means to try to escape trouble.

She prospered, despite facing prejudice along the way and, at times, racial abuse.

After World Championship and Pan American Games silver medals in 2011, she suffered heartbreak at London 2012, retrospectively disqualified after initially winning a preliminary bout for a blow judged to be an illegal chop.

Silva recovered to win the following year's world title here in Rio de Janeiro and her home city proved a happy hunting ground once again today.

"It was very difficult to overcome the problems from 2012 but I insisted that judo is my life and [I received] support from my coach and my family and the Brazilian people," she said afterwards.

"People would taunt me saying that my place was as a monkey in a cage but I insisted that my place was in sports and in judo.

"Fans have always encouraged me, especially the kids from my home community in the City of God.

"I had a dream and those kids have dreams too - I always insisted on pursuing my dreams."

Silva had used all her nous and experience gained through her London 2012 heartbreak by scoring early and then preventing her opponent from regaining a foothold in the contest.

A fanatical and knowledgable crowd surely gave her an extra boost and her win was greeted by a carnival-like atmosphere and trademark Brazilian passion.

It was still a good result for Dorjsuren, who improved upon a bronze at the World Championships last year and claimed Mongolia's first medal of Rio 2016.

Portugal's Telma Monteiro finally claimed an Olympic medal after five World Championship podium finishes.

She shared the bronze medal with Kaori Matsumoto of Japan.

Greater success followed for Japan as they finally claimed a first Rio 2016 gold medal in the judo courtesy of Shohei Ono in the under 73kg division.

The two-time world champion was a class above his rivals throughout, producing a waza-ari and then an ippon to sweep past Azerbaijan's Rustam Orujov in the final.

It marked Japan's first lightweight gold since Kenzo Nakamura won the old under 71kg event at Atlanta 1996.

"I was practising hard in Japan to get in good shape," he said.

"But it was diffiicult to show the level of my practice in the Olympic Games

"I felt a lot of pressure, but I could do it."

London 2012 under 66kg champion Lasha Shavdatuashvili of Georgia took the bronze medal, along with Dirk van Tichelt of Belgium.