West Ham United made it two wins out of two in the Europa League after goals by Declan Rice and Said Benrahma secured a 2-0 home victory over Rapid Vienna while Leicester City suffered a 1-0 defeat at Legia Warsaw on Thursday.
Italian league leaders Napoli crashed to a shock 3-2 home loss to Spartak Moscow and 1967 European Cup winners Celtic were humbled 4-0 at home by Bayer Leverkusen.
Olympique Marseille's home game with Galatasaray, which ended in a 0-0 draw, was marred by crowd trouble with play held up for eight minutes in the first half after rival fans hurled fireworks at each other.
West Ham twice hit the woodwork before England midfielder Rice turned in Michail Antonio's cross in the 29th minute and Benrahma sealed the win in stoppage time with a crisp low shot.
The result put the Hammers top of Group H on six points, three ahead of Dinamo Zagreb who thrashed Genk 3-0 away helped by two goals from striker Bruno Petkovic.
Legia emerged as the surprise Group C leaders on six points after Mahir Emreli's goal sunk Leicester.
Spartak, second on three points, fought back having fallen behind after 11 seconds when a sloppy error by goalkeeper Aleksandr Maksimenko allowed Eljif Elmas to fire Napoli ahead.
The home side had defender Mario Rui sent off in the 30th minute for a rash tackle and Spartak turned the match round thanks to two goals from Quincy Promes and another by Mikhail Ignatov.
Victor Osimhen pulled one back for Napoli in stoppage time, too late to spare Napoli coach Luciano Spalletti his first defeat in all competitions after taking over in May.
Leicester and Napoli have one point each from their opening two games.
Leverkusen goalkeeper Lukas Hradecky produced a string of superb saves against Celtic in Group G and the hosts were punished by clinical finishing at the other end.
Piero Hincapie fired the visitors ahead in the 25th minute and Florian Wirtz doubled the lead with a neat finish before Lucas Alario's penalty and Amine Adli completed the rout.
Real Betis also celebrated their second successive win as they beat Ferencvaros 3-1 in Budapest to stay level with Leverkusen on six points.
Rangers completed a poor night for Scottish clubs as they slipped to a 1-0 defeat at Sparta Prague in Group A, with Lyon keeping pole position after a Karl Toko Ekambi brace helped them to a 3-0 victory over Brondby.
Marseille and Galatasaray both missed chances in an ill-tempered Group E match, and Lazio beat Lokomotiv Moscow 2-0 thanks to first-half goals from Toma Basic and Spanish defender Patric.
(Writing by Zoran Milosavljevic; Editing by Ed Osmond)
