Mesut Ozil helped Arsenal to a 2-0 Champions League win over Napoli on Tuesday while Neymar was the centre of attention as Barcelona edged Celtic 1-0 in Scotland.
Germany midfielder Ozil scored the opening goal, his first for Arsenal, with a superb left-foot effort from the edge of the penalty area after eight minutes and set up Olivier Giroud for the second after 15.
Any lingering doubts that the former Real Madrid player was worth the $60 million that Arsene Wenger paid for him in August were swept away.
Wenger said he could not remember the last time his side, who lead the Premier League by two points, had played as well as they did in the first 45 minutes.
"It was a fantastic first half. I am delighted, it was a very enjoyable game to watch," the manager, who celebrated 17 years at the club this week, told a news conference.
Of Ozil's performance, he said: "You should just sit there and enjoy it. We are lucky to have him."
Arsenal's second win after their 2-1 success in Marseille put them on six points in Group F alongside Borussia Dortmund, who beat Marseille 3-0 on Tuesday.
Barca’s win over Celtic in Glasgow put them top of Group H with six points.
There was a moment of controversy when Celtic captain Scott Brown was sent off for kicking Neymar while the Brazilian was on the ground, but replays suggested a deliberate kick even if Neymar looked to have overreacted.
Down to 10 men in the second half, Celtic succumbed to Fabregas’ neat header from Alexis Sanchez’s cross, and remain bottom.
Brazil midfielder Ramires scored twice as Chelsea got their Champions League Group E campaign back on track with a 4-0 demolition job on Steaua Bucharest at the National Arena.
Slick-passing Chelsea, surprisingly beaten at home 2-1 by Swiss club Basel last month, dominated from start to finish and could have won by a bigger margin.
"We played good football with intelligence and maturity away from home," manager Jose Mourinho told Sky Sports television.
"I think we are going to do it (qualify for the knockout stages). This result today is important because we had to win."
Chelsea and Basel have three points from two games while Steaua are bottom of the group on zero.
Schalke 04, who won 1-0 at Basel on Tuesday, have a maximum six points. Greenpeace protesters interrupted the match in Switzerland when they dropped down on ropes from the stadium roof and unfurled a banner protesting against tournament sponsors Gazprom.
Play was halted for around five minutes when four protesters wearing orange boiler suits and helmets descended slowly on ropes which they had dropped from the roof after a few minutes of play.
The banners said "Gazprom, don't foul the Arctic" and "Free the Arctic 30" and had Greenpeace written at the bottom.
The protesters then hauled themselves back onto the roof while officials watched from the touchline and the match continued.
Russian authorities detained all 30 members of the pressure group who were aboard icebreaker the Arctic Sunrise when they broke up attempts to scale state- run Gazprom's Prirazlomnaya offshore oil platform on September 18.
All 30 have been remanded in custody for two months.
Gazprom are sponsors of both the Champions League and Schalke.
A clinical late goal from Atletico Madrid's Turkey midfielder Arda Turan gave the La Liga front runners a 2-1 win over Portuguese champions Porto in their Group G match at the Dragao Stadium.
Porto's defence was caught napping with five minutes left when Gabi slotted a clever short free kick into the area for Turan, who blasted home to steal all three points.
Initially the hosts had Atletico on the back foot with intense pressing high up the pitch and they deservedly opened the scoring through Jackson Martinez's flying header from Josue's pinpoint free kick after 16 minutes.
But Atletico equalised just before the hour mark when defender Diego Godin headed into an empty net after towering above the Porto defence having beaten onrushing goalkeeper Helton to the ball from a free kick.
Atletico's win courtesy of Turan's late strike puts them three points clear of Porto at the top of Group G on six. Zenit St Petersburg and Austria Vienna each picked up their first point in a 0-0 draw in Russia earlier on Tuesday.
Mario Balotelli converted an injury-time penalty to rescue a 1-1 draw for AC Milan minutes after hosts Ajax Amsterdam looked to have snatched an unlikely win in their Group H tie.
It was a frenetic finish to a match of few chances as both sides battled in midfield before defensive lapses led to two late goals.
Balotelli coolly converted with virtually the last kick of the match, following a controversial decision by Swedish referee Jonas Eriksson to penalise Mike van der Hoorn.
The substitute defender looked more the victim than the aggressor as he tangled with Balotelli in the area.
The penalty, four minutes into stoppage time, came after Ajax had taken the lead through central defender Stefano Denswil in the 90th minute.
He rose unchallenged to head home a Lasse Schone corner, one of just eight efforts on goal in a cagey encounter at the Amsterdam Arena.
Milan go second in Group H on four points, two behind leaders.
Ajax are third having picked up their first point of the campaign after losing 4-0 to Barcelona on the opening matchday.