The Catalans had lost their last six games against Bayern but outplayed the six-time winners at the Olympic stadium with Robert Lewandowski also on the scoresheet, while England star Harry Kane struck for the visitors.

Hansi Flick, who was in charge of the Bundesliga side in a humiliating 8-2 romp over Barca in 2020, led the Catalans to an emphatic triumph which indicated they may be capable of winning the trophy for the first time since 2015 after a decade of disappointment.

Defeat leaves Bayern with only one victory from their opening three group games and in the bottom half of the table, while Barcelona have two wins and are in the top third.

"In my opinion this game could have been a (Champions League) final, to be able to win it in this way, so well, in front of our fans, is quite special and I leave here happy," Raphinha told Movistar.

"Getting the second victory in the Champions League was important and now we have to think about the game on Saturday."

Barcelona visit European and Spanish champions Real Madrid in a La Liga Clasico this weekend and warmed up for it in spectacular style.

Flick brought midfielder Fermin Lopez in for his first start of the season after injury, while his Bayern counterpart Vincent Kompany opted for Serge Gnabry in place of Jamal Musiala, who was only fit enough for the bench.

Barcelona had not scored in their last four matches against Bayern but were ahead inside one minute, with Lopez playing Raphinha in behind the visitors' high line.

The Brazilian winger, on his 100th appearance for the club since joining from Leeds, and proudly sporting the captain's armband, stayed cool to dribble around Manuel Neuer and roll home.

Former Tottenham striker Kane had a similar chance to equalise at the other end but took a heavy touch and Inaki Pena raced out of his goal to deny him, before the Englishman had a goal ruled out for a marginal offside.

Bayern kept pouring forward and Kane found the net once more after 18 minutes, and this time it counted.

The striker finished acrobatically from Gnabry's inviting cross with Barcelona's defence all at sea.

Relentless Raphinha

Barcelona recovered their composure and began to threaten, with former Bayern striker Lewandowski firing wide and Lamine Yamal sliding in to tackle Neuer but seeing the ball roll beyond the post.

Joshua Kimmich was booked for taking out Lopez, who was charging into space in Bayern territory.

The Barcelona midfielder, a ball of energy, created his team's second for Lewandowski. Lopez left Kim Min-jae for dead with a clever nudge, which Bayern complained about to no avail, before knocking the ball across for Lewandowski to turn home.

The veteran Polish striker, 36, has been the chief beneficiary of Flick's arrival after struggling last season and now has 15 goals in 13 appearances.

The unstoppable Raphinha rattled home a superb third before the interval, driving into the area after Marc Casado spread the play out to the left flank and arcing a shot through Dayot Upamecano's legs and beyond the reach of Neuer at full stretch.

Raphinha completed his hat-trick 10 minutes into the second half, controlling Yamal's ambitious pass brilliantly on his chest while on the sprint, before planting a rasping effort into the bottom right corner from the edge of the box.

Kompany reacted with a quadruple substitution, bringing on four household names in Musiala, Kingsley Coman, Leroy Sane and Leon Goretzka.

At 4-1 up Barcelona's fans began to cheer their team's passes as Bayern chased the ball.

Having not reached the Champions League semi-final since 2019, belief is starting to grow in Catalonia that Flick could help restore their position among Europe's elite.

Another test of that theory soon follows with the impending visit to the Santiago Bernabeu.

Brazilian winger Vinicius Junior netted a treble for Madrid on Tuesday against Dortmund but his compatriot Raphinha matched him in style against Bayern as Barca sent a message of their own.