Lionel Messi scored twice as Barcelona proved they are still a major European force despite the loss of Neymar with a 3-0 Champions League mauling of last season's beaten finalists Juventus.
Messi, fresh from his derby hat-trick against Espanyol at the weekend, scored either side of an Ivan Rakitic goal as Barca put the Italian champions to the sword at the Nou Camp.
The victory comes on the back of a 100 per cent start to Barca's LaLiga campaign - during which they have yet to concede a goal - and offers an emphatic response to anyone doubting their trophy credentials following the Â£200million sale of Neymar this summer.
Neymar is also flourishing at his new club Paris St Germain, who made a similarly ominous start to their bid for a first European Cup crown with a 5-0 thrashing of Celtic at Parkhead.
The Brazil forward and fellow summer signing Kylian Mbappe - who combined are set to cost PSG in excess of Â£366million - were both on the scoresheet before fellow forward Edinson Cavani added a third from the penalty spot just before half-time.
An own goal from Mikael Lustig made it 4-0 before Cavani wrapped up the scoring with his second five minutes from time.
Bayern Munich, who are in Group B along with PSG, were 3-0 winners over 10-man Anderlecht at the Allianz Arena.
Visiting midfielder Sven Kums was sent off after conceding the 11th-minute penalty which Robert Lewandowski netted to put Bayern ahead, and then second-half goals from Thiago and Joshua Kimmich completed a comfortable win.
Premier League champions Chelsea, back in European competition after a one-year absence, inflicted a 6-0 demolition on Qarabag at Stamford Bridge.
Pedro, Davide Zappacosta, Cesar Azpilicueta, Tiemoue Bakayoko and Michy Batshuayi were on the mark before a combination of Batshuayi and visiting defender Maksim Medvedev resulted in Chelsea netting a sixth.
That result gave Antonio Conte's side the early advantage in a tough-looking Group C, with Roma and Atletico Madrid playing out a goalless draw in the night's other match.
Europa League holders Manchester United brushed aside the challenge of Basle at Old Trafford with Marouane Fellaini, Romelu Lukaku and Marcus Rashford earning a 3-0 victory for Jose Mourinho's men.
That left the Red Devils top of Group A just ahead of CSKA Moscow, who were 2-1 victors over Benfica in Portugal. Haris Seferovic put the hosts ahead but Vitinho's spot-kick drew CSKA level before substitute Timur Zhamaletdinov netted a 71st-minute winner.
Sporting Lisbon held off a late fightback to beat Olympiacos 3-2 in Greece. First-half goals from Seydou Doumbia, Gelson Martins and Bruno Fernandes put Sporting in control and Felipe Pardo's brace right at the end was not enough to save Olympiacos.