UEFA on Tuesday hit Greek side PAOK Salonica and Rapid Vienna of Austria with heavy fines and a three-year suspended exclusion from European competition after their fans clashed last week.
Riot-trained police used tear gas to stop fighting fans of both sides ahead of their UEFA Europa League playoff round first leg in Salonica on Thursday. PAOK won the game 2-1.
UEFA reacted quickly, saying: "The Greek and Austrian clubs have been disqualified for one competition in progress and/or excluded from the next competition for which they qualify in the next five years. The bans for the two clubs are each suspended for probationary periods of three years."
PAOK were ordered to play their next three UEFA competition home matches behind closed doors, and fined 150,000 euros ($188,000) after being charged with the "improper conduct of supporters, including crowd disturbances, pitch invasion, setting off and throwing of missiles and fireworks, and insufficient organisation".
Rapid Vienna also faced charges of improper conduct of supporters and were fined 75,000 euros, and must play their next UEFA competition home game behind closed doors.
UEFA added that the punishment did not apply to the UEFA Europa League play-off second leg between Rapid Vienna and PAOK in Vienna on August 30.
The two have three days in which to appeal the UEFA rulings.