Returning Paris Saint-Germain forward Ousmane Dembele called on his teammates not to let up after a goal rout over Bayer Leverkusen in Tuesday's 7-2 away Champions League win.

The Champions League holders, who have won three from three to start their title defence, scored six of their seven goals with 10 men, having lost Illia Zabarnyi to a red card late in the first half.

Desire Doue, man of the match when PSG thumped Inter Milan in the Champions League final in Munich in May, relished his return to Germany, scoring twice before half-time.

Ballon d'Or winner Dembele was only fit enough for the bench but scored just three minutes after coming onto the pitch midway through the second half.

Willian Pacho, Khvicha Kvaratskhelia, Nuno Mendes and Vitinha also scored in a statement win for the French giants.

Playing his first match since claiming the Ballon d'Or last month, Dembele said his side "could have avoided our red card", but "stayed in the game and scored goals before half-time that did us good.

"And we just had to roll on in the second half. Scoring seven goals is important, we have to keep it up," he added. "It's only the first half of the season, we'll have to stay on target in Europe and the league."

The 28-year-old said he was "not at 100 percent yet" and wanted to come back in the league last weekend, but "the coach told me to wait a bit longer. I'm slowly getting my form back."

Meanwhile, Fermin Lopez bagged a hat-trick and Marcus Rashford struck twice for Barcelona in a 6-1 demolition of Olympiacos to get the Catalan giants back on track in the Champions League.

Teenage star Lamine Yamal was also on target for Hansi Flick's side, who lost against holders Paris Saint Germain in their previous European outing in the league phase.

After a Lopez double Ayoub El Kaabi pulled one back from the penalty spot for the Greek champions, but Santiago Hezze's red card allowed injury-hit Barcelona to rack up a big scoreline and go provisionally third.

Flick was without Robert Lewandowski, Raphinha and several other regulars, but his team were able to build some confidence at the Olympic stadium ahead of the Clasico against Real Madrid on Sunday in La Liga.

Erling Haaland was among the scorers in Manchester City's 2-0 win at Villarreal, while Newcastle inflicted more Champions League pain on Jose Mourinho's Benfica with a 3-0 win at St. James' Park. (AFP)