ATHENS, Greece (AP) — A Greek policeman was severely injured late Thursday when a mob of volleyball fans poured out of an Athens arena and attacked riot police outside.

State ERT television said a flare shot by a rioter severed a thigh artery in the 30-year-old officer, who was reported in critical condition at a hospital.

The violence occurred during a volleyball match between crosstown rivals Olympiakos and Panathinaikos. The game was abandoned when the fighting erupted outside the arena.

ERT said about 150 people left the arena during the game to attack riot police stationed outside with flares, gasoline bombs and stones, and then returned to the venue.

Police made heavy use of tear gas, much of which wafted into the indoor sports ground. Officers also prevented spectators from leaving the arena amid efforts to identify the person who fired the flare.

Security had been high for the game as the two clubs’ supporters have a history of intense rivalry. Greek soccer is plagued by endemic fan violence, which often spreads to other sports in which the main clubs field teams, such as basketball and volleyball.