Title-holders Paris Saint-Germain came from behind to beat Barcelona 2-1 with a last-minute goal in the Champions League on Wednesday, while Manchester City had to settle for a draw in Monaco despite Erling Haaland's double.
Elsewhere there were comfortable wins for Arsenal and Newcastle United, as Napoli and Borussia Dortmund were among the other teams to claim victories on the second matchday of the league phase.
The meeting at Montjuic of the Spanish champions and the reigning French and European champions was one of the most eagerly anticipated of the opening stages of this season's competition.
It lived up to its billing, despite Ballon d'Or winner Ousmane Dembele missing out injured for an understrength PSG, with Lamine Yamal showing flashes of his brilliance for the hosts.
Barcelona went ahead in the 19th minute as a well-worked move ended with Marcus Rashford setting up Ferran Torres to score.
Senny Mayulu equalised late in the first half for PSG, and Achraf Hakimi set up substitute Goncalo Ramos to net a 90th-minute winner as PSG made it two victories from two outings in this season's Champions League.
"It was a great game between two really good sides," PSG coach Luis Enrique told Canal Plus. "It shows the strength and mentality of our side that whoever is on the field we play like a real team."
MAN CITY HELD BY MONACO
Haaland scored twice in the first half to move to 52 career Champions League goals from 50 appearances, but 2023 tournament winners City were held 2-2 in Monaco.
Jordan Teze's stunning hit in between Haaland's strikes kept Monaco in the game until they won a late penalty as Nico Gonzalez was penalised following a VAR review for a high boot on Eric Dier.
Dier got up to convert from the spot and give Monaco their first point in the competition, denying City a second win from as many outings.
"I don't know if it was a penalty but it was given. So that's that," City coach Pep Guardiola told TNT Sports. "It is what it is. We have a point and we will take it."
Arsenal maintained their 100 per cent record with a 2-0 defeat of Olympiakos in London, with Gabriel Martinelli following in to score a 12th-minute opener after a Viktor Gyokeres attempt hit the post.
The Gunners sealed the points in stoppage time as substitute Bukayo Saka scored with a shot that squirmed under Greek goalkeeper Kostas Tzolakis.
"Winning in the Champions League is always very complicated. It is yet another clean sheet for the boys in the competition, which is remarkable," Arsenal manager Mikel Arteta said.
NEWCASTLE, DORTMUND SCORE FOUR
Earlier Newcastle got their campaign up and running by cruising to a 4-0 victory over Belgian champions Union Saint-Gilloise in Brussels.
Nick Woltemade diverted a Sandro Tonali shot into the net for the opener, his third goal in four starts for the club.
Anthony Gordon then scored two penalties, either side of halftime, before substitute Harvey Barnes wrapped up the success late on.
Dortmund were also impressive winners, as the beaten 2024 finalists tore into Athletic Bilbao, winning 4-1.
Daniel Svensson put them ahead in the first half and Carney Chukwuemeka made it two soon after the interval.
Gorka Guruzeta got one back for Athletic, but Serhou Guirassy and Julian Brandt sealed a fine win for the German club.
In southern Italy, Rasmus Hojlund bagged a brace as Napoli claimed their maiden European victory this season, beating Sporting 2-1. Luis Suarez had equalised for the Portuguese champions at one point in the second half with a penalty.
Juventus, who drew 4-4 with Dortmund in a thriller in their opening game, played out a 2-2 stalemate with Villarreal in Spain.
Georges Mikautadze gave the hosts the lead, only for Federico Gatti to equalise with an overhead kick before Chico Conceicao gave the Italians the advantage.
But Renato Veiga, who spent the second half of last season on loan at Juventus from Chelsea, headed in to earn Villarreal a draw.
Bayer Leverkusen and PSV Eindhoven drew 1-1 in Germany, with Christian Kofane giving the hosts the lead only for Ismael Saibari to equalise for the Dutch side.
Qarabag are the sensation of the competition so far, the club from Azerbaijan following a win over Benfica two weeks ago by beating FC Copenhagen 2-0 in Baku.
Abdellah Zoubir and Emmanuel Addai got their goals and Qarabag are one of six teams on six points, along with Bayern Munich, Real Madrid, PSG, Inter Milan and Arsenal.