(Adds doping cases, Ukraine gold, skating quotes)
* South Koreans complain of figure skating bias
* German biathlete, Italian bobsledder test positive
* U.S. and Canada meet in big men's ice ho6ckey clash
* Emotional biathlon relay gold for Ukraine
By Mike Collett-White
SOCHI, Russia, Feb 21 (Reuters) - A scent of scandal hung over the Olympics on Friday after two athletes tested positive for banned substances in Sochi's first doping cases while and doubts persisted over whether judges were right to give Russia gold in the women's figure skating.
In Friday's action, though, there could be few more popular winners than Ukraine's women's biathlon relay team, who took the country's first gold of the Games at the end of a week when anti-government protests left at least 77 people dead.
A Ukrainian skier had already pulled out of Sochi in protest at President Viktor Yanukovich's handling of the crisis and other athletes said they struggled to focus as their country went up in flames.
"We will not celebrate, we will be peaceful, because of what's happening in our nation," Sergey Bubka, Ukraine's Olympic head, told reporters as he fought back tears.
The emotional scenes at the Laura venue in the Caucasus Mountains were somewhat overshadowed as the first doping cases emerged three days before the end of the Games on Sunday.
German biathlete Evi Sachenbacher-Stehle, a two-times Olympic champion at cross country, tested positive for a banned stimulant and was sent home.
Hours later, Italian officials announced that bobsleigh athlete William Frullani, a policeman, also tested positive for a banned substance and was excluded from the team.
The Games had already been reeling from a contentious piece of judging in the women's figure skating that threatened to take some of the gloss off the host nation's first-ever gold in the event.
Adelina Sotnikova, who few expected to be among the medals before the contest began, beat favourite Kim Yuna late on Thursday, despite the South Korean defending champion producing a performance many viewers deemed superior.
The controversy rumbled on into Friday, when South Koreans expressed shock and anger at a decision they said had been engineered to favour the Russians.
More than 1.5 million people signed an online petition demanding an inquiry into Kim's loss, which many people stayed up into the early hours to watch. "Queen Yuna" is South Korea's most loved and best-known athlete.
It was not only her compatriots who questioned the scoring.
"How the hell were Yuna and Sotnikova so close in the components?" exclaimed Canada's four-time world champion Kurt Browning. "I just don't get it.
"Yuna Kim outskated her, full stop. I'm shocked. What, suddenly, she just became a better skater overnight? I don't know what happened. I'm still trying to figure it out."
Russian television and radio stations lionised their 17-year-old champion on Friday, and little mention was made of the judging issue.
Sovietsky Sport newspaper did refer to the scandal with the headline: "American media cast doubt over Adelina Sotnikova's victory".
ICE HOCKEY GIANTS MEET...AGAIN
Seven medals were being contested on Friday, but it was the men's ice hockey semi-finals that generated the most buzz, particularly in North America ahead of the clash of titans Canada and the United States.
The Americans will have revenge on their minds when the take to the ice at the Bolshoy Ice Dome, after Canada beat them in dramatic style in the last Olympic final in Vancouver.
In the other semi-final, Sweden beat Finland 2-1 in another gold medal rematch after the teams met in the 2006 Turin decider, also won by the Swedes.
In the medal events, Canada moved up to second in the overall table behind Norway with two more golds.
Marielle Thompson and Kelsey Serwa took gold and silver in the rough and tumble of the women's ski cross final held at the Extreme Park.
German Anna Woerner was taken off the course on a stretcher with a knee injury after a nasty fall during the quarter-finals, her leg appearing to give way on impact as she hit the icy landing slope.
Safety concerns were high after Russian free skier Maria Komissarova fractured a vertebra and dislocated her spine during practice on the same course last week.
Canada's men also won the curling, brushing aside Britain to win 9-3 and claim the country's third successive title and complete the double after their women also took gold.
The women's Alpine skiers bade farewell to the Games as American Mikaela Shiffrin won the slalom ahead of Austrian duo Marlies Schild and Kathrin Zettel.
Later on Friday and there are three more golds to be won in the unpredictable sport of short track speed skating, where the favourites can often get bumped out of contention.
South Korean-born Viktor Ahn, now competing for Russia, seeks to add to his haul of four Olympic golds in the 500 metres and 5,000m men's relay, while Elise Christie hunts Britain's first Olympic short track gold in the women's 1,000m having twice been disqualified earlier in the games.
In speed skating, the United States will depart without a medal for the first time since the 1984 Sarajevo Games, after their men's and women's team pursuit trios were both knocked out in the first round on Friday.
The U.S. team had predicted they were capable of winning eight medals prior to the Games, but their efforts may have been hampered by a fiasco over their suits when they decided to change them halfway through the Olympics to no apparent effect.
Arguably the moment of the day came in the women's biathlon, where Ukraine edged out Russia for only their second Winter Olympics title.
Given upheaval at home, in which Russia has played a major role by backing Yanukovich against pro-European protesters, it was an emotional moment as the Ukrainian flag was raised.
Russian President Vladimir Putin will be desperate for the crisis in neighbouring Ukraine not to overshadow Sochi, which he has used to project his country as a modern, tolerant state that does not deserve the Western criticism it receives.
But Russian protest group Pussy Riot, who released a music video in Sochi this week attacking the Games and Putin's human rights record, have drawn international attention to what critics say is his refusal to brook opposition.
In Moscow on Friday, a judge convicted eight defendants of assaulting police during a protest against Putin, in what activists called a "show trial".
Sentencing was postponed until Monday, however, meaning it will be revealed after Sunday's close of the Olympics. Putin says he does not use courts as a political tool. (Additional reporting by the Reuters Olympics team in Sochi and Rosa Khutor and by Ludmila Danilova and Gabriela Baczynska in Moscow. Editing by Mitch Phillips.)