ATHENS — In a landmark trial reckoning with the extreme far right, a Greek court Wednesday found Golden Dawn party leaders and lawmakers guilty of running a criminal organization — an extraordinary rebuke of a party that had once clawed into the country's mainstream.

Thousands of Greeks outside the courthouse cheered the ruling, which also included specific guilty findings for attacks on immigrants and the murder of an anti-fascist rapper.

The ruling all but cements the fall of Golden Dawn, a party that a decade earlier had grown on the back of Greece’s financial and migrant crises and presaged the rise of other, less extreme European nationalist parties.

In the verdict, which followed a trial lasting more than five years, 18 top members of the party were found guilty of being part of a criminal organization. Seven, including the leader, Nikos Michaloliakos — who once claimed there were no gas chambers in Auschwitz — were found guilty of running a criminal organization.

They have not yet been sentenced.

Many outside observers had portrayed the trial as an example of a democratic country grappling with its most hardcore political faction. Greece is now governed by a center-right party, and far-right sentiment has receded to the margins. But the trial was a chance to look back on what happened during a decade of severe tumult, when the economy was collapsing and migrants were arriving in historic numbers, creating resentments that Golden Dawn saw as an opportunity.

Although Europe has seen the rise of many far-right parties, few — if any — have been as overtly fascist as Golden Dawn. Activists and prosecutors, and many politicians, describe the party as a neo-Nazi organization. Its logo echoes the swastika. Soon after the party’s founding in the 1980s, an official party magazine described Adolf Hitler as “the great man of the 20th century.”

As late as 2009, the party had virtually no electoral support. But by 2012, amid debt crises and austerity measures, Golden Dawn was the Greece’s third-largest party, holding 18 of the 300 seats in Parliament.

Golden Dawn tried to win support from the neediest citizens, setting up food distribution and blood banks while making clear that the generosity was for “Greeks only.”

But prosecutors argued that, even as its members sat in Parliament, the group was essentially a paramilitary criminal organization, orchestrating street violence, attacks on immigrants and the 2013 murder of Pavlos Fyssas, a rapper who was also known for anti-fascist activism. A self-professed Golden Dawn member, Giorgos Roupakias, was found guilty Wednesday of the killing.

The murder set off widespread public opposition to the party, and, as members stood trial, defections and poll defeats further weakened it. Golden Dawn no longer holds any seats in the Greek Parliament.

“In the conscience of the Greek people they are a criminal organisation and will go where they deserve go, in the trash can of history,” Alexis Tsipras, the Greek prime minister from 2015 until 2019, wrote on his official Facebook page after the verdict was announced.

The violence examined during the trial mostly took place between 2010 and 2013. Prosecutors showed photos of Golden Dawn recruits at training camps posing with assault weapons and giving Nazi-like salutes.

The party’s leaders had promised to rid Greek society of its “stench” — a term they used to refer to immigration. Some activists saw Golden Dawn’s hand in a spate of attacks on foreigners.

“Golden Dawn successfully exploited the system to lawfully enter Parliament, but at the same time kept its neo-Nazi identity. This was a point of admiration for extremists worldwide,” said Vassiliki Georgiadou, a professor of political science at Panteion University in Athens.

Although the party has splintered, other small far-right parties have been trying to fill the void. And many Greeks still resent what they see as an unfair migration burden — with other European countries unwilling to help host newly arrived asylum seekers.

“History has shown that most of Golden Dawn’s voters were driven by circumstances and condemn the party’s extremism,” Georgiadou said. “Immigration, however, will continue to drive nationalist sentiment in Greece. This remains a worrying trend that can only be resolved if Europeans work together to provide solutions. For extremism to stop, it must not be given space to grow.”

Greece’s hard left celebrated the verdict, with some anti-fascist activists represented in the crowd outside the courthouse.

Prime Minister Kyriakos Mitsotakis portrayed the court decision as a victory for the entire political spectrum.

“Αfter the Greek people voted the neo-Nazi party of Golden Dawn out of parliament in the last election, today the Greek justice system convicted its leadership of operating as a criminal organization,” he said on Twitter. “A truly historic day for Greece, democracy and the rule of law.

Harlan reported from Rome.