Marseille marked their return to the Uefa Champions League after seven years with a 1-0 loss at Olympiakos
Andre Villas-Boas' men wore black armbands during the Group C game at the Georgios Karaiskakis stadium to honour Samuel Paty, the teacher who was murdered in Conflans-Sainte-Honorine last Friday after showing pictures of the Prophet Mohammed to his pupils.
Marseille succumbed in second-half stoppage time on Wednesday night to Ahmed Hassan's strike after he was set up by the former Marseille playmaker Mathieu Valbuena.
In the same group, Manchester City came from behind to beat Porto 3-1.
Luis Diaz gave the visitors the lead at the Etihad Stadium after 14 minutes but Sergio Aguero levelled from the penalty spot midway through the first-half.
Pep Guardiola's men took control after the pause. Ilkay Gundogan gave City the lead and Ferran Torres sealed the victory 11 minutes from time.
Elsewhere Bayern Munich began the defence of their title with a 4-0 win over Atletico Madrid in Group A
Kingsley Coman, who scored the winner in the final against Paris Saint-Germain in August, got Bayern's first and Leon Goretzka fired in the second just before half-time.
Corentin Tolisso added the third in the 66th minute and Coman grabbed his second of the game six minutes later.
In Group D, there were wins for Liverpool and Atalanta over Ajax and FC Midtjylland respectively while in Group B Shaktar Donetsk stunned Real Madrid 3-2 and Romelu Lukaku scored a stoppage equaliser as Inter Milan drew 2-2 against Borussia Monchengladbach.