The United States triumphed at last week's tournament in Malaga, moving on to 40 points at the halfway stage of the series, and a hat-trick from Jaz Gray propelled them to a 52-0 thrashing of debutants Portugal in their Pool A opener at the Estadio Olímpico de la Cartuja.

Gray was on the scoresheet again as the US followed it up with a 24-10 win against England, who also look well positioned to progress to the quarter-finals after triumphing 33-12 over Canada in their first match.

Australia top the series standings on 56 points after winning both events in Dubai, and eased past Belgium 38-0 in Pool C before beating hosts Spain 26-7 in the final match of the day.

They are tied with France on six points, after the Tokyo 2020 Olympic silver medallists kept two clean sheets in scoring 43 and 45 against Spain and Belgium, respectively.

France and Russia both have 46 points from the first three events, and the runners-up in Malaga clinched comfortable 26-7 and 29-5 wins against Brazil and Poland respectively in Pool B.

Ireland were the fifth side who finished the day unbeaten after also beating those two opponents to book their place in the quarter-finals.

One of the highlights of the opening day of the men's tournament came in the Pool A clash between Spain and the US, who are fourth for the season.

The Americans held a 14-0 lead, but Spain hit back, and a second try from Tobias Sainz-Trapaga - converted by Juan Martinez - had them on the brink of a shock victory.

However, the US kept the ball alive from the restart for a Carlin Isles try to level the scores at 26-26, with Stephen Tomasin adding the extras to clinch a dramatic win 90 seconds into overtime.

Olympic bronze medallists Argentina, who have earned a medal at each of the three tournaments so far this season, saw off Jamaica 42-0 in Pool B.

Ireland came from behind to beat Germany 33-5 in the other match in that pool.

After a third-place finish in Malaga, England started with a 28-10 win against Japan in Pool C, with France overcoming Wales 38-12 in the other match.

In Pool D, Australia secured their biggest-ever World Rugby Sevens Series win by hammering Kenya 42-0, while Scotland defeated Canada 21-5 in the first men's match of the day.

South Africa, who have won all three events this season, were handed a bye in their Pool A opener with Samoa unable to compete because of COVID-19 travel restrictions.

The pools are set to conclude tomorrow and be followed by the quarter-finals in Seville.