(CNN) - A league game between Greek football giants Panathinaikos and Olympiakos had to be abandoned after 70 minutes on Sunday as fans clashed with both players and police.
Olympiakos, the visiting team at Panathinaikos' Olympic Stadium, was leading the Athens derby 1-0 when German referee Marco Fritz was forced to bring an end to proceedings.
The match was initially stopped for eight minutes within just six minutes of the game kicking off, with a group of home team supporters -- some of whom were masked -- invading the outside of the pitch and attacking the Olympiakos substitutes and those in the team's dugout.
The referee added 13 minutes of first-half stoppage-time to make up for the lengthy incident.
The game's only goal -- scored in the 53rd minute by Spanish striker Miguel Angel Guerrero -- sparked further violence, this time outside the stadium, with fans releasing firebombs.
Police fought back using teargas in an attempt to put an end to the fighting and to regain control. However, the fumes then wafted into the arena and spread onto the pitch, hitting the players and the fans within the stadium.
Some fans then filtered from the stands onto the athletics track around the perimeter of the field.
As a result, Fritz called off the remainder of the game with 20 minutes remaining, with many of the 25,000 Panathinaikos fans who had attended the fixture already having left due to the effects of the teargas.
'I have no words'
Olympiakos, who led at the time and continue to chase down PAOK, the Thessaloniki-based club at the summit of Greece's Super League domestic top flight, has been awarded the victory and three crucial points.
Panathinaikos, meanwhile, could face the possibility of a fine and points deduction.
Olympiakos midfielder Kostas Fortounis told his club's official website afterwards: "It's tragic, I cannot explain it.
"Getting into the stadium, chasing the players, our agents... I have no words. After the goal we put in, the fans came on the pitch.
"We could not continue the game. The players of Panathinaikos went to calm them, but they [the fans] were not [calm]."
Panathinaikos also issued a statement, criticizing the actions of a "small minority of 25,000 fans."
Fritz was only in charge after a 2018 ruling decreed that foreign referees would be imported to oversee potentially controversial matches in the nation's Superleague.
This came after FIFA demanded that Greek football made a series of urgent reforms, following a series of unruly, violent incidents.
After a late goal was disallowed in a game between AEK Athens and PAOK last season, PAOK owner Ivan Savvidis stormed onto the pitch armed with a gun. He later received a three-year ban from football and PAOK was docked three points.
A scheduled match between Olympiakos and Panathinaikos' basketball teams on Saturday was forfeited by Olympiakos, who refused to take on its rival without a foreign referee.
'Derby of the Eternal Enemies'
The fixture between the two most successful clubs in Greek football history is known as the 'Derby of the Eternal Enemies' and this was the latest in a long line of incidents to spill from the clubs' ferocious rivalry.
Indeed, fans of visiting teams are not allowed to attend games in Greece as a result of the country's history of fan violence and unrest.
In March 2012, nine police officers were injured after serious riots broke out between Panathinaikos fans and police after supporters without tickets attempted to enter the stadium for the derby.
The match was ultimately abandoned after petrol bombs were set off in the stands and firebombs thrown at police outside the arena. Firetrucks entered the stadium in order to put out the fires -- including one on the ground's electronic scoreboard, but they were also attacked by fans.
In March 2014, the clash between the sides was marred when then-Panathinaikos manager Yannis Anastasiou fell to the ground after being hit with an object hurled from the crowd.
In February 2015, the top division was temporarily suspended by the Greek government after trouble marred another clash between the two Athens giants.
Yet, later that year in November, the game was called off after fans fought with riot police before the game had even kicked off. After the decision to cancel the match, fans invaded the pitch, while broken chairs and advertising hoardings were thrown onto the field.
Just three months ago, the league was suspended for a week once again, after referee Thanasis Tzilos was assaulted outside his home.
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