Barcelona kicked off the defence of their Champions League crown with a 1-1 draw away to Roma.
After an evenly-contested opening at the Stadio Olimpico, Barcelona took the lead on 21 minutes when Luis Suarez headed home Ivan Rakitic's cross from close range.
Roma felt Lucas Digne, the defender on loan from PSG, was fouled in the build-up, and that Suarez converted the chance from an offside position, but referee Bjorn Kuipers was unmoved and the goal was allowed to stand.
The Giallorossi were soon level, though, as right-back Alessandro Florenzi's audacious 60-yard effort sailed over Marc-Andre ter Stegen in the Barca goal before cannoning into the back of the net off the post.
Barca worked tirelessly in a largely uneventful second half to regain the lead, but they were unable to breach a resolute Roma rearguard, with Lionel Messi coming closest to scoring when he rattled the crossbar on 78 minutes.
The visitors mounted a late rally in search of the winner but Roma stood firm to claim a morale-boosting draw with the European champions.
Elsewhere in Group E, former Manchester United striker Javier Hernandez scored his first goal for Bayer Leverkusen in their 4-1 victory over Belarusian champions BATE Borisov.
Hakan Calhanoglu struck twice for the Bundesliga club after Admir Mehmedi opened the scoring at the BayArena, before Hernandez scored the Germans' third.
The visitors had drawn themselves level through Nemanja Milunovic's first-half effort, but Leverkusen saw out the victory to move top of Group E on three points.
Bayern Munich maintained their 100 per cent start to the season as two goals from Thomas Muller and a strike from substitute Mario Gotze sealed an impressive 3-0 victory away to Olympiakos.
Muller beat Olympiakos 'keeper Roberto with what looked like an intended cross from out on the right flank after 52 minutes.
The hosts battled but they could not find an equaliser as Bayern sealed the win with a late Gotze effort, quickly followed by Muller's second.
Vitaliy Buyalskyi came off the bench to score a late equaliser for Dynamo Kiev as they were held to a 2-2 draw at home to Porto.
After a two-year absence from the group stages, Kiev, who were paired in group alongside Premier League champions Chelsea, made a great start when Oleg Gusev scored after 20 minutes.
Porto were level three minutes later when Vincent Aboubakar out-jumped his marker and he put the visitors in front after the break following a corner.
But Buyalskyi was on hand to save Kiev, racing onto Serhiy Rybalka's mis-hit drive and firing past Iker Casillas.
Competition newcomers Gent overcame the disadvantage of two dismissals to come from behind and draw 1-1 with Lyon in Group H.
Gent finished with nine men but goalkeeper Matz Sels made a one-handed penalty save just two minutes from time to ensure a share of the spoils in a drama-filled tie at the Artevelde Stadium.
The Belgian club's Champions League debut almost turned into a nightmare after Brecht Dejaegere was sent off four minutes before half-time, with Lyon opening the scoring 13 minutes later when substitute defender Christophe Jallett expertly headed home a corner.
But the lead lasted just 10 minutes before Danijel Milicevic equalised for the hosts. However, with two minutes left, Thomas Foket was dismissed for a tug on Lyon's Aldo Kalulu and Lyon were awarded a penalty.
Alexandre Lacazette, seeking to end a recent goal drought, stepped up to take the spot kick but saw Sels stick up his hand to turn the effort over the crossbar.
Elsewhere in the group, two first-half goals from Hulk guided Zenit Saint Petersburg to an impressive 3-2 victory at Valencia.
An Axel Witsel own-goal on 54 minutes sparked the fightback for the hosts, however, with Andre Gomes levelling the tie with 17 minutes remaining.
But Witsel atoned for his error to have the final say, striking with 14 minutes remaining to give Zenit a maiden triumph in Spain.
Wednesday's Champions League results:
Group E: Bayer Leverkusen 4-1 BATE Borisov, Roma 1-1 Barcelona
Group F: Dinamo Zagreb 2-1 Arsenal, Olympiakos 0-3 Bayern Munich
Group G: Dynamo Kiev 2-2 Porto, Chelsea 4-0 Maccabi Tel Aviv
Group H: Valencia 2-3 Zenit Saint Petersburg, Gent 1-1 Lyon