Olympiakos Piraeus and Montpellier will both face a disciplinary hearing over the crowd trouble which marred their Champions League match on Tuesday, UEFA said in a statement.
The Greek side has been charged with use of laser beams against players by their supporters, throwing of missiles and «insufficient organization (lack of body search),» during its 3-1 win, UEFA said.
The French visitors were charged with crowd disturbances and «setting off and throwing of fireworks».
Media reports said around 100 Montpellier fans clashed with riot police before the Group B game. The hearing will take place on November 22.
UEFA said Olympiakos would also face action over the «improper conduct of the team», a charge which is brought automatically against any side which receives five or more yellow cards in a game.
Greek soccer has been beset by crowd violence. In a recent case, PAOK was ordered to play its next three European matches behind closed doors following a riot at a Europa League qualifier at home to Rapid Vienna in August.
PAOK will also have to pay a 150,000-euro fine and face automatic expulsion from European competition if there is a repeat incident within the next three years. Fans of PAOK and Rapid hurled a variety of firecrackers and other missiles at each other, and at one point dozens of masked fans ran onto the pitch.