Novak Djokovic marked his return to action with a dominant 6-0 6-1 victory over Greece's Ioannis Xilas to put Serbia in control of the Davis Cup tie. (More Tennis News)

The 24-time major winner was playing his first match since his US Open third-round defeat by Alexei Popyrin at Flushing Meadows a fortnight ago.

And Djokovic, who helped his nation win the Davis Cup in 2010, looked close to his best as he dropped just a single game, while converting five of the seven break points he forced.

Wrapping up a dominant victory in just 45 minutes, he put Serbia 2-0 to the good in the World Group I tie.

Elsewhere in that group, Casper Ruud helped Norway wrap up a 3-1 win over Portugal.

The three-time major finalist, who put his nation 2-1 to the good alongside Viktor Durasovic in the doubles rubber, was a 7-6 (7-3) 6-2 victor over Jaime Faria in their singles clash.

Later in the day, Argentina booked their place in the final eight after Maximo Gonzalez and Andres Molteni saw off Finland in the doubles decider.