Besiktas are to contest a UEFA ban, handed down for the crowd trouble which marred their Europa League fixture at Lyon, while the Ligue 1 club are considering their response to a sanction of their own.
Last Thursday's quarter-final first leg at Parc Olympique Lyonnais was delayed by 45 minutes after fans streamed onto the pitch, seeking refuge from objects being hurled from the tier above them, which housed the travelling Turkish fans.
Both clubs were fined €100,000 on Wednesday and banned from the next UEFA competition for which they qualify in the instance of repeat offences within the next two years.
There was also a pitch invasion by home fans after Jeremy Morel took advantage of a mistake by Besiktas goalkeeper Fabri to secure a 2-1 Lyon win.
Besiktas will host the second leg of the tie on Thursday and the Turkish club hit back at the charges from UEFA.
"The decision taken by UEFA regarding the match played in Lyon cannot be justified and accepted by our club," a statement said. "We will follow the process by making the necessary objections to UEFA.
"We must avoid all kinds of negative behaviour that can leave Besiktas in a difficult situation in international arenas by showing respect to the rivalry without allowing provocation."
Lyon were also involved in further crowd issues in their Ligue 1 game at Bastia at the weekend as kick-off was delayed after Bastia supporters confronted Lyon players on the field during the warm-ups and the match was later abandoned following further disturbances.
President Jean-Michel Aulas praised the response to last week's crowd trouble, while stopping short of confirming whether Lyon had accepted the sanctions, or planned to contest them.
"I've got the good idea to join the fans in the stands where they were chased and fought by the other fans," Aulas said.
"We've had a good reaction. If we had not done that, the game wouldn't have been played. We'll see if we appeal. But first, it's a sanction we assume."