Fans were forced onto the pitch prior to Lyon's Europa League match against Besiktas after projectiles were thrown between the sets of supporters.
Kick-off in the quarter-final first leg was delayed as supporters sought refuge on the pitch of Parc Olympique Lyonnais. The projectiles came from the upper tier of the stadium, where fans of Besiktas were housed.
Security staff and local police were, however, on the scene to escort the spectators back to their seats and the match eventually kicked off at 21:50 local time – 50 minutes late.
Lyon tweeted out a picture of the scenes with the caption: "Projectiles and fireworks launched from the top of the stands require supporters to seek refuge on the pitch."
With the players on the pitch for warm-ups, travelling Turkish fans and home supporters began to clash. UEFA spokesman Pedro Pinto tweeted that the game would be delayed due to "crowd disturbances".
The disruption, which comes just two days after a bomb attack on the Borussia Dortmund team bus in Germany, followed earlier clashes in the Lyon city centre between the sets of supporters.