South Africa on Saturday defeated the United States 42-7 to win the opening event of the HSBC World Rugby Sevens Series season at the Dubai Sevens at the Sevens Stadium.

It was South Africa's eighth victory in Dubai and extended their winning streak in the HSBC World Series to 18 matches.

Victory also secured a third consecutive Series gold medal for the defending Series champions following wins in Vancouver and Edmonton.

Ronald Brown scored a hat-trick of tries and added five conversions for a 25-point haul. Brown's teammates JC Pretorius, Selvyn Davids and Shaun Williams also scored a try each with Branco du Preez kicking the final conversion.

Lucas Lacamp scored the lone try for the United States with Steve Tomasin adding a conversion.

Meanwhile, Olympic semi-finalists Argentina defeated a new-look Fiji team 19-12 in the bronze final to claim third place.

Elsewhere, the women's event saw Australia beat Fiji 22-7 in the final while Olympic silver medalists France hammered France 40-0 in the third/fourth place playoff.

The next leg of the Series will take place between December 3-4, again, at the Sevens in Dubai.

(With input from agencies)