The tournament began on Thursday with 18 finalists set to compete in six groups of three across three cities - Madrid, Turin and Innsbruck. Eight teams qualify for the knockout rounds with the final taking place in Madrid on December 5.

Elias hit 22 winners as he eased past Steven Diez 6-4 6-2 in the first match before younger brother Mikael made it 2-0 with a solid 6-4 6-4 victory over Vasek Pospisil.

The Swedes then won the doubles for a convincing 3-0 win.

Mikael was impressive on serve, winning 80 per cent on points on his first serve and facing just one break point.

"When you play someone like Vasek who's so good in his offence it doesn't give me, especially with my toolbox, it doesn't give me a lot of other options than to try to counter," said the 23-year-old ranked 93 in the world.

"And I think the serve helped a lot today to not give him too many looks, especially in my service game."

The Czech Republic's Tomas Machac caused a huge upset in his Davis Cup debut when the 21-year-old, ranked 143 in the world, beat France veteran Richard Gasquet 7-6 (7-3) 6-2.

But the Czechs' joy was shortlived as France bounced back for a 2-1 win in Innsbruck, with Adrian Mannarino downing Jiri Vesely 6-7 (7-1) 6-4 6-2 and the doubles pairing of Pierre-Hugues Herbert and Nicolas Mahut getting the better of Jiri Lehecka and Machac, winning 3-6 6-4 6-3.

In Turin, former US Open champion Marin Cilic and Borna Gojo spearheaded 2018 victors Croatia's 3-0 win over Australia.

Gojo fired eight aces to secure a 7-6 (7-5) 7-5 victory over Alexei Popyrin, who is 215 rungs above the Croatian in the ATP rankings.

Cilic edged past Alex de Minaur 6-1 5-7 6-4 in the second rubber.

De Minaur and John Peers were then thumped 6-3 6-1 by the world's No.1 pairing, Olympic champions Nikola Mektic and Mate Pavic.

Meanwhile, Spanish player Carlos Alcaraz has tested positive for the coronavirus and will miss Spain's upcoming Davis Cup finals campaign, which begins in Madrid on Friday against Group A opponents Ecuador.

Davis Cup officials tweeted on Thursday a player had gone into isolation and the 18-year-old Alcaraz revealed on Instagram he was the man in question and very sad to "miss such an important and special event."

The other Spanish players are conducting a new round of PCR tests.

ATP Cup winners Russia are also in their group, with world No.2 Daniil Medvedev and world No.5 Andrey Rublev in the team.

Australian Associated Press