Erling Haaland scored twice after half-time as Manchester City began their campaign with a 2-0 victory over FC Porto at the Estadio do Dragao.
Both sides had made commanding starts to their domestic seasons and entered the UEFA Champions League knowing that only a maximum return would be considered a satisfactory beginning to the tournament.
After a goalless first half, Manchester City broke the deadlock five minutes after the restart. New signing Enzo Fernandez produced a moment of quality before setting up Haaland, who headed the ball against the inside of the near post and into the net.
The Norway striker struck again in the first minute of stoppage time, creating room inside the penalty area before finishing a cross from Rayan Ait-Nouri. The goal was Haaland’s 59th in the competition.
He has now scored five times in four matches in all competitions for City this season.
Real Madrid also opened their league-phase campaign with a win, beating Inter Milan 2-1 at Santiago Bernabeu on Tuesday evening.
The new-look Los Blancos are beginning their pursuit of a record-extending 16th Champions League title and needed a response after losing to Real Betis on Friday.
Inter began brightly and looked to take the game to the hosts, but a mistake from Yann Bisseck allowed Real Madrid to seize the initiative. Kylian Mbappe took advantage to put the home side ahead.
Another defensive error then increased Inter’s problems. Goalkeeper Josep Martinez failed to deal with a back-pass, giving Federico Valverde the opportunity to intervene and make it 2-0.
Both teams created further chances and there were impressive saves at either end before Inter reduced the deficit inside the final 10 minutes. Carlos Augusto converted from close range, but Real Madrid held on and claimed all three points.
Elsewhere, Real Betis recovered from going behind twice to beat 10-man LOSC Lille 3-2 and make a winning start to their European campaign.
Betis arrived in confident mood after their morale-boosting victory over Real Madrid in LaLiga on Friday, but the visitors were behind after 12 minutes when Ayase Ueda finished to give Lille the lead.
Marc Bartra restored parity in the 33rd minute with a well-directed header, only for Alexsandro Ribeiro to put the French side back in front three minutes later with another headed finish from a corner.
The visitors turned the match around early in the second half. Bartra completed his brace with a second header before Troy Parrott ran on to a through pass and found the bottom corner to complete Betis’ comeback.
Lille’s evening deteriorated further when Ethan Mbappe was shown a straight red card following an off-the-ball incident. The dismissal was confirmed after a review by the Video Assistant Referee.
Borussia Dortmund also began with victory, edging an entertaining contest against Villarreal 3-2.
The Black and Yellow took the lead 10 minutes into the second half when Renato Veiga turned a left-wing cross into his own goal.
Villarreal responded around the midway point of the half, with Santiago Mourino heading a cross into the bottom corner to level the score.
Dortmund regained control during the final five minutes as Serhou Guirassy scored twice, including once from the penalty spot.
Guirassy was unfortunate to put through his own net at the other end in the final moments after sending a ball into the area following a free-kick. It did not prevent the Bundesliga side from securing the win.
