Manchester City overcame an early scare to get their Champions League defence off to a solid start on Tuesday, as Europe's top club competition made a breathless return.

City were stunned when Red Star's Osman Bukari opened the scoring in first-half stoppage time, but Julian Alvarez continued his sparkling early season form by levelling just two minutes after the break.

Alvarez bagged a second when goalkeeper Omri Glazer flapped at the Argentine's free-kick, allowing the ball to fly into the far corner. Rodri rounded off the 3-1 win with a composed finish 17 minutes from time.

Also in Group G, RB Leipzig's Mohamed Simaken earned the distinction of scoring the first goal of the group stages, with the competition only three minutes old.

The French-born defender's header put the Austrian side into a lightning lead against Young Boys, in Berne. Elia levelled for the Swiss hosts, but second-half strikes from Xaver Schlager and Benjamin Sesko wrapped up a 3-1 win for Leipzig.

At Parc des Princes, Kylian Mbappe set PSG up for a 2-0 victory over Borussia Dortmund, in a daunting Group F.

The French champions went ahead four minutes after the break when Mbappe scored a spot-kick awarded for a Niklas Suele handball. Achraf Hakimi added a memorable second.

"It was an almost perfect evening," purred new coach Luis Enrique.

PSG's next date is at Newcastle, whose manager Eddie Howe was proud of his side's dogged return to the competition against seven-time European kings AC Milan, earning a goalless draw at the San Siro.

In Catalonia Joao Felix struck twice as Barcelona flexed their muscles with a crushing 5-0 win over Royal Antwerp to show their determination to be considered among Europe's elite once again.

Felix shone for the Spanish champions in the Catalan capital, helped on their way by an own goal, with Robert Lewandowski and Gavi also scoring.

That lifted them top of Group H from Porto, 3-1 winners over Shakhtar Donetsk.

Over in Rotterdam, a "bitterly disappointed" Celtic manager Brendan Rodgers was left to rue the "inexperience" of two players sent off in their 2-0 loss to Feyenoord, but said the Scottish champions had proved they could be competitive during their Group E clash.

Midway through the second half defender Gustaf Lagerbielke was shown a second yellow card after pulling back Brazilian striker Igor Paixao in the box. He was barely down the tunnel when substitute Odin Thiago Holm also saw red for a studs up late challenge.

And in Rome, Lazio goalkeeper Ivan Provedel scored a stunning 95th minute header to secure a point in a 1-1 draw against Atletico Madrid. (AFP)