The build-up to Lyon's Europa League quarter-final meeting with Besiktas was marred by the throwing of projectiles and firecrackers that forced fans onto the Parc OL pitch on Thursday night.
Both sets of players had emerged to warm up when objects began to rain down from the stands, causing an unexpected delay to the start of proceedings in France.
Alongside an image of supporters entering the field of play, Lyon posted a tweet reading: "Projectiles and firecrackers thrown from the tops of the stands have forced fans to take refuge on the pitch."
The match was expected to kick off at 8.05pm BST, but Uefa spokesman Pedro Pinto tweeted that there would be a delay due to "crowd disturbances".
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