Fans clashed on the pitch last night after the game, which ended 1-1, and incidents before the match saw a reported five fans - four Belgians and a Spaniard - arrested.

Anderlecht coach Ariel Jacobs played down the pitch invasion, attributing it to the "euphoria" following the result which gives the Belgian outfit the edge in their last-32 tie.

"I want to thank the Anderlecht fans who have covered so many kilometres to give their support to the team," he said.

"I think the invasion was due to a state of euphoria and it is regrettable."

UEFA have yet to react but they are expected to come down hard after fining Austria Vienna 20,000 euros and ordering them to play two games behind closed doors - one suspended - following incidents in their match against Athletic in December.