Champions League holders Paris Saint-Germain stunned Barcelona with a 90th-minute Goncalo Ramos winner to claim a 2-1 away victory in the league stage on Wednesday.

Ferran Torres sent Hansi Flick's Barcelona ahead with a cool finish but Senny Mayulu fired a depleted PSG level before half-time.

It was an even and thoroughly entertaining bout between two of the competition's favourites at the Olympic stadium which was eventually settled by Ramos' late strike, as PSG exploited Barca's high defensive line.

"After scoring the (first) goal we got a confidence boost and in the second half we were better," Luis Enrique told reporters.

"I'm happy... because it's an important victory and playing against Barcelona is always difficult."

Luis Enrique, who won the treble coaching Barcelona in 2015, was lacking several key players and his team held on at times but eventually got the better of last season's semi-finalists.

"If you let in a goal in the last minute and you lose at home, you're going to be disappointed," Barcelona midfielder Frenkie de Jong told Movistar.

"There's a long way to go in the Champions League. It was a good game to test where we are -- we have to improve. We know that and we will do it."

Barcelona and PSG have not been on the best of terms over the past decade, with the Catalans recording one of the sport's greatest comebacks in 2017 with a 6-1 win over the Parisians.

PSG snatching Neymar and going on to sign all-time Barca great Lionel Messi worsened relations, although Luis Enrique's approach and a spate of injuries left the visitors shorn of star names on their return to Catalonia.

Ballon d'Or winner Ousmane Dembele and his usual attacking partners Desire Doue and Khvicha Kvaratskhelia all missed out, but PSG midfielders Vitinha and Fabian Ruiz were fit to start.

From kick-off Barca starlet Lamine Yamal was out to prove a point. After finishing as runner-up behind Dembele, the teenager started stating his case for next year's award.

Yamal pirouetted away from two defenders and dodged Nuno Mendes, starting an enthralling battle with PSG's left-back.

The defender shut him down for Portugal in the Nations League in the summer and managed to dispossess the winger in the box a few minutes later to strike back in their individual tussle.

Yamal created the first clear chance with a sensational pass using the outside of his boot to send Torres through.

The Spaniard rounded goalkeeper Lucas Chevalier but Illia Zabarnyi slid in to block his goal-bound effort.

Barcelona took the lead in the 19th minute after Yamal and Pedri combined and Torres slotted home from Marcus Rashford's quick first-time pass.

PSG started to grow into the game and forced Wojciech Szczesny into his first save, tipping Achraf Hakimi's free-kick around the post.

Mendes gave Yamal a taste of his own medicine by blazing away from the youngster downfield, cutting through Barcelona players, only to be felled by a desperate De Jong.

Mendes repeated the trick to set up the equaliser, tearing into Barca territory. Pau Cubarsi misjudged a lunge to try and cut out his pass for 19-year-old striker Mayulu, who beat Szczesny in the 38th minute.

- Marauding Mendes -

Bradley Barcola fired narrowly over and then forced Szczesny into a solid save either side of the interval as the European champions clicked into a higher gear.

PSG were fortunate Mendes was not issued a second yellow for felling Yamal in full flow on the edge of the box as the pendulum swung back the other way.

Dani Olmo's shot was cleared off the line by Hakimi and PSG's Kang-in Lee curled against the post as the clock ticked down and Barca started to tire.

Eventually Ramos grabbed three points for PSG as he stayed onside to collect Hakimi's pass, after the Moroccan got in behind Barca's defence, and slot home.

"We're happy with what we showed today," said Luis Enrique, after PSG sealed their second win from two league stage games.

The coach hailed his full-backs Mendes and Hakimi, calling them the finest in their positions in the world.

"No doubts, the two best," added Luis Enrique. "Nuno and Hakimi played excellently."