Celtic and Manchester City shared six goals in a thrilling 3-3 draw in Glasgow.
The home side got off to a dream start in the Group C clash when, with three minutes gone, Scott Sinclair's free kick was played back across goal and Erik Sviatchenko's header flew in off Moussa Dembele.
City levelled when a deflected shot by Kolarov broke for Fernandinho and his control and low finish put the visitors on terms with only 12 minutes gone.
But Celtic were back in front again when Kieran Tierney, overlapping on the left, smashed a low effort in off Sterling as he tried to get back and cover -- only for Sterling to grab an equaliser at the other end.
Within moments of the start of the second half, the Scottish champions led for the third time as Dembele steered an overhead kick past Bravo -- but City were unbowed and Nolito tied the game up for a third time after a flowing move.
Arsenal, fresh from the weekend's 3-0 win at home to Chelsea, won 2-0 against Basel in Group A with a dominant display at the Emirates.
The Gunners started brightly and were rewarded after six minutes when a ball down the left freed Alexis Sanchez, whose fine cross was headed in by Theo Walcott.
And Walcott struck again as a lovely move involving Mesut Ozil and Sanchez freed him to arrow a low finish in at the far post, with the Gunners -- and particularly Sanchez -- spurning numerous chances to add to their tally.
Last season's runners-up Atletico Madrid beat Bayern Munich 1-0 in Spain, but Antoine Griezmann suffered a repeat of his missed penalty in the final.
Bayern had the first real chance of the Group D clash when a superb dinked Thiago pass was chested down and volleyed by Thomas Muller, who saw his effort well saved.
Fernando Torres then hit the post from close range -- but the home side broke through when Yannick Carrasco broke through the defence to fire past Manuel Neuer and in off the post. Griezmann could have doubled their lead but saw his penalty crash back off the woodwork.
Barcelona recovered from a goal down to win 2-1 at Borussia Monchengladbach and take another three Group C points.
La Liga's champions, who had seen an early Neymar effort saved, trailed when Thorgan Hazard struck after 21 minutes, converting a Mahmoud Dahoud pass.
They were back on terms soon after the hour when Neymar chipped into the area and, with the goalkeeper hesitating, Arda Turan thumped a volley into the roof of the net. And they sealed the points when Gerard Pique pounced on a rebound after goalkeeper Yann Sommer failed to hold a Suarez volley.
Two goals from Edinson Cavani and a penalty save by Alphonse Areola helped Paris Saint-Germain to a 3-1 victory at Ludogorets in Group A.
The French champions' uncertain start to the season threatened to continue as they found themselves behind after 16 minutes when Natanael curled a free kick through an unconvincing wall and past Areola.
But they drew level thanks to a fine finish from Blaise Matuidi and went ahead after the break when Cavani glanced home a header. Areola then stopped a Cosmin Moti penalty and the hosts were made to pay as another Cavani effort was deflected home.
Rostov and PSV shared four goals in Group D in a 2-2 draw in Russia.
After a scrappy opening, Rostov took the lead with their first group stage goal -- sidefooted home by Dmitry Poloz -- but the Dutch side levelled when Davy Propper's deflected effort left goalkeeper Soslan Dzhanayev stranded.
Rostov restored their lead before the break when a long ball forward was headed down and, from the edge of the area, Poloz sent a bouncing half-volley into the corner to score his second goal of the game.
Luuk De Jong equalised in scrappy fashion right on half-time, bundling home a header after a deflected cross had cannoned back off the bar -- but they missed a golden chance to take the lead when Propper saw his penalty saved by Soslan Dzhanayev.
Napoli won 4-2 at home to Benfica, with the Group B visitors closing the gap after finding themselves four down before the hour mark.
Marek Hamsik opened the scoring after 20 minutes with a near post header from a corner -- and after the break Dries Mertens curled home a free-kick and Milik added his second from the penalty spot after goalkeeper Julio Cesar had brought down Jose Callejon.
A fourth goal followed within a matter of moments as Mertens also made it two goals on the night with a close-range finish after the ball rebounded to him off Milik, but Goncalo Guedes and Eduardo Salvio hit back.
Besiktas and Dyanmo Kiev shared the points in another Group B clash with a 1-1 draw in Turkey.
Besiktas took the lead in style as Ricardo Quaresma whipped a 25-yard free kick into the top corner top left-hand corner.
But midfielder Viktor Tsygankov equalised when a free kick from the right was allowed to run all the way across goal and the substitute fired home.