Heavyweights Barcelona and Bayern Munich edged towards the knockout stage of the Champions League on Wednesday 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.
"We have won our first three matches, and this is an important achievement," a delighted Carrasco said.
"We had to work really hard for this win, against difficult opponents...We are in good form, playing well and keeping things tight in defence."
Arsenal turned in the performance of the night to thump Ludogorets 6-0, with a first career hat-trick for Mesut Oezil.
"Our confidence is stronger with every win but we have to keep the vigilance as well, and the urgency to bring that into the next game," Arsenal manager Arsene Wenger said.
"Let's not be too quick on the verdict. We have a strong squad and a strong spirit, but you have to take care of it and keep your feet on the ground. The only way to win something big is to focus on the next one and work on humility."
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.
Guardiola said the key factor in the defeat was the red card for keeper Bravo, in the 53rd minute for handling the ball outside the penalty area, after passing the ball with his feet.
"After the card it was over...We were there, we were in the game. We were pressing, we had the possession and we made the chances. We did it but we didn't take the chances and you have to do that to win the game
"We knew from the beginning it would be a tough group, and it is certainly proving to be so."
Barca defender Mathieu was also sent off, for a second needless yellow card offence.
Barca's Neymar had a penalty saved by Bravo's replacement Willy Caballero, but made amends with a handsome late strike to complete the 4-0 rout.
The only bad news for Barca was that defenders Jordi Alba and Gerard Pique both limped off injured.
"These injuries are a setback for us, but nonetheless it was a good night," Barca coach Luis Enrique said.
"Whoever had any doubts about Messi's fitness and form has been proved wrong.
"It was a rather strange game, what with mistakes, sendings-off, injuries...This is a great result, one which will strengthen us."
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. Napoli have six points, Besiktas five, Benfica four and Kiev just one.