Two late goals in two minutes from Sergi Roberto and Luis Suarez gave Barcelona a remarkable 2-1 home win over Bayer Leverkusen in Champions League Group E.
Trailing 1-0 with 10 minutes to go, Sergi poked in a rebound from close range, and moments later Suarez swept the ball home from just inside the area.
Kyriakos Papadopoulos put the German side ahead after 22 minutes from a corner, with Barca keeper Marc-Andre Ter Stegen beaten in the air.
For reigning champions Barca, who were without their injured talisman Lionel Messi, it was a frustrating game of missed chances until their pressure told.
Barca have four points from two games in Group E and Leverkusen have three.
Elsewhere, Bayern Munich striker Robert Lewandowski continued his remarkable scoring run with a hat-trick in a 5-0 thrashing of Dinamo Zagreb to snap the Croats' 45-game unbeaten run and take control of their Champions League group.
|Lewandowski had scored five goals in nine minutes in a league match last week [EPA]
In an explosive first half in which Bayern were 4-0 up inside half an hour, Lewandowski, who has notched a staggering 10 goals in their last three matches, netted twice in seven minutes after Brazilian Diego Costa had put Bayern ahead.
Mario Goetze added his second of the campaign before Poland captain Lewandowski chipped keeper Eduardo in the 55th minute for his third goal as the title favourites moved to a maximum six points from two Group F matches.
Jose Mourinho suffered a nightmare homecoming as Porto, the club he led to the Champions League title in 2004, inflicted a 2-1 defeat on his woefully out-of-sorts Chelsea side.
Mourinho sprang a surprise before the game by leaving out Eden Hazard, Nemanja Matic and Oscar and the Londoners went behind after 39 minutes when Yacine Brahimi produced a surging run down the left and Andre Andre scored.
Brazil playmaker Willian equalised with the last move of the first half, curling a delightful free kick into the top corner of the net from 25 metres.
Porto then went back in front seven minutes after the break when Maicon stooped low at the near post to head a left-wing corner past keeper Asmir Begovic.
Porto 2-1 Chelsea
Maccabi Tel Aviv 0-2 Dynamo Kiev
Arsenal 2-3 Olympiakos Piraeus
Bayern Munich 5-0 Dinamo Zagreb
BATE Borisov 3-2 AS Roma
Barcelona 2-1 Bayer Leverkusen
Olympique Lyon 0-1 Valencia
Zenit St Petersburg 2-1 Ghent