Olympiakos beat Panathinaikos in derby
Goals from Kevin Mirallas after 20 minutes and Rafik Djebbour in the 90th took Olympiakos 10 points clear at the top of the Super League with just seven matches to go.
Torosidis was sent off in added time for a headbutt on Panathinaikos's scorer Leto as tempers boiled over and dozens of Olympiakos supporters ran onto the pitch at the final whistle.
Four Panathinaikos players were harassed by the home fans as they tried to reach the dressing rooms including French striker Djibril Cisse who has threatened to quit the country.
"These are the last few months you'll see me in Greece," he told reporters. "Under these kinds of conditions I can't continue to play here."
The kick-off was held up for several minutes due to dense smoke from the dozens of flares lit by Olympiakos fans.
Once the match got underway the home side dominated the first half while Panathinaikos were on top in the second. Former Olympiakos midfielder Leto scored just before the hour to cancel out Mirallas' opener and both sides then missed chances.
Referee Dimitris Kalopoulos controversially ruled out an effort by Panathinaikos's Kostas Katsouranis for offside in the 82nd minute before Djebbour scored the last-gasp winner.
Panathinaikos were unhappy with the referee's performance and issued a strongly-worded statement after the match.
"Unfortunately, instead of talking about football, today we have to condemn a clear unjust result and the undeniable deterioration of the league," it said.
"A perfectly legitimate goal was cancelled and two clear penalty decisions were not given in our favour.
"There are not words in the Greek language to describe the refereeing performance of Mr Kalopoulos."