American teenager Mikaela Shiffrin made Winter Olympics history by becoming the youngest slalom gold medal winner at Rosa Khutor Alpine Center.

The 18-year-old from Colorado was the favourite heading into the event after topping the podium at last year's World Championship in Schladming and was the overall World Cup champion.

She proved she could shine on the grandest stage on Friday with an opening run that left her nearly half a second clear of the rest of the field.

Shiffrin, who finished fifth in the giant slalom earlier this week, set off second time around with a healthy 1.34second advantage over second-placed Marlies Schild, and although she nearly fell halfway through her run, she held her nerve to move into the record books.

An overall time of one minute 44.54 seconds was enough to secure victory by 0.53secs ahead of silver medallist Schild, whose fellow Austrian Kathrin Zettel claimed bronze.

"It is tough to describe my feelings. This has been a dream of mine for a very long time," Shiffrin said after breaking Paoletta Magoni-Sforza's record for the youngest Olympics slalom winner.

Ukraine stormed to an emotional gold in the women's 4x6km team biathlon, finishing 26.4 seconds ahead of nearest challengers Russia.

Olena Pidhrushna, on the anchor leg for Ukraine, hit every target in the final shoot to race clear of Russia's Olga Vilukhina down the stretch.

Norway came home in bronze medal position, 37.6 seconds behind the Ukrainians.

The Ukrainian quartet of Vita Semerenko, Juliya Dzhyma, Valj Semerenko and Pidhrushna had led the field from the end of the second leg, when Dzhyma overtook Olga Zaitseva after the Russian made a costly mistake in her standing shoot.

Neither Valj Semerenko nor Pidhrushna surrendered the lead over the final 12km as the team secured Ukraine's first gold in Sochi in what was an emotional victory following the recent deadly protests in Kiev.

"Before the race people wrote us many messages and wishes, waiting for victory," Pidhrushna said.

"Until the very last moment, even this morning I read my emails, saying like 'girls, start and win for us all, for Ukraine'. We are so happy that the people of Ukraine are happy back home and that something good happened for our country."

Canada were crowned men's curling champions following a comprehensive 9-3 defeat of Great Britain in the final.

Brad Jacobs' rink led 6-2 after five ends and continued to add the points until David Murdoch's British team called it a day at the end of the ninth.

Sweden won a dramatic bronze-medal play-off against China 6-4 after an extra end, in a match which saw the Asians penalised for two technical violations.

Marielle Thompson underlined her status as favourite for the women's ski cross by taking gold at Rosa Khutor Extreme Park.

The 21-year-old Canadian capped a fantastic season, that has seen her secure two wins and four podiums from seven World Cup races, by topping the standings in Sochi with a deserved victory, where she came first in all four of her races on Friday.

Compatriot Kelsey Serwa was on Thompson's heels for the entirety of the final but had to settle for silver, while Sweden's Anna Holmlund took bronze.

In the short track, Victor An skated off with two gold medals as Russia enjoyed a bumper night in the Iceberg Skating Palace.

An claimed his first victory in the men's 500 metres final, seeing off competition from China's Wu Dajing and Canadian Charle Cournoyer.

The South Korean-born skater then helped Russia take gold in the men's 5000m relay, joining up with Semen Elistratov, Vladimir Grigorev and Ruslan Zhakarov in beating the United States and China.

The success marked An's third gold medal of the Games.

South Korea's Park Seung-Hi secured gold in the women's 100m final, ahead of China's Fan Kexin and compatriot Shim Suk Hee.