Dortmund in seventh heaven after thrashing Celtic

Karim Adeyemi starred as Borussia Dortmund ran riot against Celtic, while Barcelona and Manchester City claimed their first wins in the restructured Champions League.

Adeyemi scored a first-half hat trick as Dortmund routed Celtic 7-1 at home on Tuesday (Wednesday AEDT).

Robert Lewandowski got Barcelona off the mark as the Spanish giants eased to a 5-0 home win over Swiss team Young Boys, while his former teammate İlkay Gundogan helped City to a 4-0 win at Slovan Bratislava. Manchester City's Erling Haaland scored his 42nd goal in his 41st Champions League game.

City were held 0-0 by Inter Milan in their opening game, while Barca responded to their 2-1 loss at Monaco, the team's first defeat under new coach Hansi Flick.

Mikel Arteta's Arsenal outclassed his former team Paris Saint-Germain 2-0, with Kai Havertz and Bukayo Saka scoring in the first half for the Gunners.

Arteta enjoyed a successful 18-month loan spell at PSG while he was still a teenager at Barcelona.

In other results, Inter Milan defeated Red Star Belgrade 4-0, and Bayer Leverkusen defeated AC Milan 1-0 in Germany.

Daniel Braganca scored late to earn Sporting Lisbon a 1-1 draw at PSV Eindhoven.

Stade Brest had never played in the Champions League before this season. On Tuesday, the French team routed Salzburg 4-0 away for their second win in as many games in Europe's premier competition.

Senegalese forward Abdallah Sima netted twice to take his tally to three goals in two games after he scored in Brest's tournament-opening 2-1 win over Austrian champions Sturm Graz.

Mahdi Camara and Mathias Pereira Lage got the other goals, ensuring Salzburg conceded seven goals in their opening two games, after losing 3-0 at Sparta Prague in their opener.

Kaan Kairinen's brilliant free kick was enough for Prague to draw 1-1 at Stuttgart in Tuesday's other early game.

Stuttgart fans displayed a huge sign saying "Back in Europe" behind one of the goals. It was the team's first Champions League match at home since a 1-1 draw with Barcelona in February 2010, when Zlatan Ibrahimovic scored for the visitors.

The Stuttgart fans didn't have to wait long on Tuesday before Enzo Millot headed in the team's first real chance in the seventh minute, but Kairinen equalised with a free kick in off the top of the right post in the 32nd minute.

Stuttgart, who lost their opening game 2-0 at defending champions Real Madrid, needed goalkeeper Alexander Nubel at his best.

This is the first season since the Champions League underwent a major shake-up, with four more teams added and the group stage scrapped in favour of a league system, with each team playing eight opponents once.