Ahn Hyun-soo won his second gold medal of the Winter Olympics after clinching the men's 1000m speed skating title.
Ahn just edged the gold medal on the finishing line
The Korean, who won the 1500m last week, set a new Olympic record with a time of one minute 26.739 seconds.
Ahn's compatriot Lee Ho-Suk was edged into silver, while Apolo Anton Ohno of the USA claimed the bronze medal.
Jin Sun-yu led a South Korean one-two in the women's 1500m final, while Great Britain's Sarah Lindsay was knocked out in the semi-finals.
The Koreans had thought they had completed a clean medals sweep when Choi Eun-kyung and Byun Chun-sa crossed the finishing line behind their 17-year-old compatriot.
But Byun was disqualified for impeding, leaving China's 500m champion Wang Meng to claim bronze.
Lindsay squeezed into the semi-finals, where she finished last of six in her race.