Real Madrid survived a second-half fightback from Inter Milan to begin its UEFA Champions League campaign with a 2-1 victory on Tuesday, while Erling Haaland struck a brace to lead Manchester City to a 2-0 win over FC Porto. 

Kylian Mbappe gave Real the breakthrough after 14 minutes, taking advantage of some sloppy play from Inter. Federico Valverde then doubled the advantage nine minutes later, dispossessing goalkeeper Josep Martinez before the ball rolled into the net. 

Inter responded by putting Real under sustained pressure and forcing goalkeeper Thibaut Courtois into a series of saves on the Belgian's 100th Champions League appearance.

Carlos Augusto eventually reduced the deficit in the 77th minute after meeting a cross from Lautaro Martínez, but Jose Mourinho's side resisted Inter's late push to secure all three points.

The result provided a welcome response for Real following the club’s 1-0 La Liga defeat to Real Betis last Friday which was Mourinho's first loss in his second stint in charge of Los Blancos. Inter will be frustrated to have left Spain with a loss after causing the Spanish giants trouble.

The new-look City side also collected three points on the opening night with a 2-0 victory at Porto as key striker Haaland was once again on song.

Porto goalkeeper Diogo Costa frustrated City throughout the opening half, making several saves as the visitors searched for a breakthrough. The resistance lasted only two minutes after the interval, when Haaland met Matheus Nunes' delivery with a header to put City in front.

The Norwegian returned in stoppage time to finish a move created by Rayan Ait-Nouri and put the result beyond doubt.

Haaland's double lifted his career total in the competition to 59 goals from the same amount of games and gave Enzo Maresca a victory on his Champions League debut with City.

Elsewhere, Borussia Dortmund and Real Betis both emerged with victories in five-goal contests. Serhou Guirassy struck twice, including from the penalty spot, as Dortmund defeated Villarreal 3-2, while Betis overturned a two-goal deficit to win by the same score at Lille. Marc Bartra scored twice for the Spanish side before Troy Parrott completed the turnaround, with Lille later reduced to 10 men following Ethan Mbappe's dismissal.

Aston Villa also earned a 3-2 away victory, overcoming Club Brugge through goals from John McGinn, Emiliano Buendia and the club's new signing Nicolas Jackson despite the Belgian side's strong second-half response. Villa goalkeeper Zion Suzuki made history in the game as he became the first ever Japanese goalkeeper to feature in the Champions League. In Athens, Razvan Marin scored the only goal of the game via a first-half free-kick as AEK Athens beat Champions League debutant LASK 1-0.