The violence erupted with 7:03 remaining in the second quarter and Panathinaikos leading 26-17.
Panathinaikos' Stefan Lasme tangled with Pero Antic under the basket and headbutted his opponent, earning a technical foul. Olympiakos fans responded by throwing various objects onto the court, with one hitting Panathinaikos' Greek-American guard Mike Bramos, who was sitting on the bench. Fans then ran onto the court and exchanged blows, forcing riot police to intervene — at one point using stun grenades. Olympiakos fans tried to storm the VIP section and tore off seats which they threw at the police.
The referees stopped the game and declared, despite objections from both clubs, that they would not restart it until the stands were evacuated. Some people remained in the VIP section, along with the media, the riot police and security staff.
Authorities, fearful of violent incidents, had already limited fan attendance at the Hellinikon arena to 900 from each team. The arena seats 8,000 at present, but its capacity at the 2004 Athens Olympics, when it hosted men's and women's basketball preliminaries, was 14,500.
The fans were placed at opposite ends of the arena, separated by hundreds of riot police. But some fans still threw flares before the game, one of which hit Olympiakos forward Kyle Hines during warmups. Hines was unhurt.
Dimitris Diamantidis led Panathinaikos with 19 points in the game and Roko Ukic added 18. Antic paced Olympiakos with 17.
Panathinaikos jumped out to a 17-5 lead to start the game and was ahead 41-30 at halftime. But Olympiakos cut into the lead in the second half and took its first lead of the game at 72-71 with 3 minutes left.
But Ukic restored the lead with a basket and a free throw, and Panathinaikos didn't trail again.
Violence has become commonplace at Greek sports events, whether football, basketball, volleyball or even water polo, with fan clashes sometimes turning deadly. Greek clubs typically compete in several sports, making it harder for police to contain violent fan rivalry. In 2007, hundreds of rival fans of Panathinaikos and Olympiakos clashed outside a women's volleyball game. A 25-year-old supporter died after being stabbed numerous times and beaten on the head with a bat.
As a result of the frequent violence, visiting team fans are not allowed to attend games in men's football and basketball.
Violence has been far less frequent at international games played in Greece because sports federations have imposed heavy sanctions on Greek teams in the past, including fines and suspensions from competition.