US swimmer Ryan Lochte bagged two golds on the opening day of the world short-course championships to add to the five medals he won in the London Olympics.
The American led from start to finish to win the men's 200-metres freestyle before teaming with Anthony Ervin, James Feigen and Matthew Grevers to win the 100m freestyle relay.
China's teen Olympic sensation Ye Shiwen finished second to Britain's Hannah Miley in the women's 400m individual medley.
Lochte was pushed hard by Germany's world record holder Paul Biedermann in the 200m freestyle, but he clocked 1min 41.92sec to claim his 15th career world short-course championships gold medal.
The second gold was secured in a much tougher contest and needed anchor-leg swimmer Grevers to chase down Russia's Artem Lobuzov and then hold off the late charge of Italy's Filippo Magnini to secure Lochte's 16th gold medal in the championships history.
Those two golds saw the US team sit atop the medals standings at the end of day one, with the women adding a third gold by winning the final race of the day, the 200m freestyle relay.
The quartet of Megan Romano, Chelsea Chenault, Shannon Vreeland and Allison Schmitt were pushed all the way by Russia, but Schmitt's greater strength over the final 200m brought them home in front.
Elsewhere it was a good day for eastern European women. Hungary's Katinka Hosszu set a competition record of 2:02.20 when she won gold in the 200m butterfly and in doing so became the first Hungarian woman to win a medal in championship history. She also finished third behind Miley and Ye in the 400m individual medley.
Lithuania's 15-year-old Olympic champion Ruta Meilutyte meanwhile twice broke the championship record on her way to the 50m breaststroke final. In the morning session she finished in 29.56 and then lowered it 29.51 in the semi-final.