Romanian judoka Alina Dumitru stunned hot favorite Ryoko Tani in the semi-finals, then won the 48kg category gold in imperious fashion Saturday.

The four-time European champion beat Cuba's Yanet Bermoy emphatically in the final, dumping her opponent on the tatami to score uko within the first 50 seconds, and then throwing her for an automatic ippon victory with minutes left.

Romania's Alina Alexandra Dumitru celebrates after winning the gold medal in the women's 48kg judo event against Cuba's Yanet Bermoy yesterday. [Agencies]

She caused a bigger sensation in her semi-final bout against Tani, Japan's two-time Olympic champion, who had not been beaten in a major international competition since 1996.

However, Dumitru was not intimidated by her illustrious opponent, who was penalized thrice for passivity, and took the upset win.

Tani did claim a record fifth Olympic medal by taking a bronze as she beat Russia's Liudmila Bogdanova with ippon.

Argentina's Paula Pareto also took bronze, albeit in controversial fashion, after referees overruled a waza ari awarded to her Democratic People's Republic of Korea opponent Pak Ok-song, and gave it to her instead.

The score, awarded at the end of the match, prompted jeers and wolf-whistles from spectators, and saw referees leave the tatami to confer with officials.

Pak slumped to the tatami after referees overruled the score, and had to be coaxed back to bow and shake hands with Pareto.