Heavyweights Barcelona and Bayern Munich edged towards the knockout stage of the Champions League with home thrashings of Manchester City and PSV Eindhoven respectively.
Barca trounced City - who had goalkeeper Claudio Bravo sent off - 4-0, with a hat-trick from the fit-again Lionel Messi, while Bayern downed PSV 4-1 thanks to strikes from Thomas Mueller, Joshua Kimmich, Robert Lewandowski and Arjen Robben.
Bayern are three points behind Group D leaders Atletico Madrid, who won 1-0 in Rostov on a goal from Yannick Carrasco.
Arsenal turned in the performance of the night to thump Ludogorets of Bulgaria 6-0, with a first career hat-trick for Mesut Oezil.
In the same Group A, Paris Saint-Germain crushed Basel 3-0.
Borussia Moenchengladbach won 2-0 at Celtic, Benfica prevailed 2-0 at Dynamo Kiev and Napoli surprisingly crashed 3-2 at home to lively Besiktas.
The main attraction of the night was Barca's clash with City, now coach by former Barca boss Pep Guardiola.
It was Guardiola's second return to the Camp Nou since his departure in 2012, the first being a 3-0 drubbing with Bayern Munich in 2015.
Things went even worse for Guardiola this time, with Messi shaking off his recent hamstring problems to bang in his 37th hat-trick for Barca, taking advantage of some sloppy defending from the visitors.
Barca are top of Group C with maximum nine points. City have four, Moenchengladbach three and Celtic just one.
Atletico Madrid are also on nine points in Group D, with the Spanish teams in the competition having made an emphatic start.
Atletico are three points above second-placed Bayern. PSV and Rostov have one point apiece.
Meanwhile, in Group A, Arsenal and Paris share top spot with seven points each, while Ludogorets and Basel have just one apiece.
Napoli are still top of Group B despite their shock defeat against Besiktas.