STR / AFP / Getty Images Members and supporters of the ultra-nationalist Golden Dawn party chant the national anthem in front of the Greek Parliament in central Athens on May 29, 2013

In a suburb of Athens on Tuesday night, a mob of some two dozen thugs cornered Pavlos Fyssas, a well-known leftist rapper, and killed him. According to reports, one man in the crowd fatally stabbed the 34-year-old anti-fascist musician—known by his stage name Killah P—who had been reportedly watching a soccer match at a cafe with his girlfriend and some friends. Police later said they had arrested a 45-year-old man, who allegedly confessed not only to the crime, but also to being a member of the far-right Golden Dawn party, an extremist Greek nationalist group that has emerged from obscurity in recent years to become one of crisis-hit Greece‘s most potent political movements.

Golden Dawn has rejected any link to the murder, but that didn’t stave off an irate backlash. As the country braced for another round of strikes by government employees, protesting the latest E.U.-mandated austerity cuts, anti-fascist demonstrators marched throughout the country, in some instances clashing with police. International human rights monitor Amnesty International issued a stern statement, imploring the Greek government “to send a clear message that attacks like this won’t be tolerated.” And there are signs that it may indeed take action. “It is our duty not to allow any space whatsoever to fascism – not even an inch,” said Greek President Karolos Papoulias.

The toll of a six-year-long recession — and more than three years of biting austerity — has radicalized Greek politics, with public sentiment angrily aimed against the country’s establishment. From being a fringe irrelevance, the anti-immigrant Golden Dawn first won seats in parliament last year and has grown since to become the third most influential political party in Greece, polling as much as 15% support in recent surveys. And while its electoral clout has soared, Golden Dawn supporters have been implicated in a rising tide of vigilante violence, targeting immigrants and political opponents.

Its members have been seen doing everything from beating up foreign fishermen to interrupting World War II commemorations with Nazi salutes to slapping left-wing female politicians on television. The movement cloaks itself in an ultra-nationalism that gestures to the iron rule of Greece’s anti-communist military junta, which held sway in the 1960s and early 1970s. Also invoking a mythical authenticity, Golden Dawn holds annual ceremonies at Thermopylae, site of the ancient battle between Spartan hoplites and the vast armies of the Persian Empire. While Golden Dawn members vociferously deny they’re Nazis, their insignia bears a remarkable resemblance to the Nazi swastika.

Critics accuse successive center-right governments of downplaying the violence attributed to Golden Dawn in order to curry favor with the alarming number of voters drawn to the far-right. But Fysass’s death marks the first time in recent years alleged far-right thuggery has claimed a Greek national’s life. Questions now circle whether the leadership of Golden Dawn has lost control of its rank-and-file. Greece’s deputy prime minister demanded Wednesday that Golden Dawn be treated like a “criminal gang,” echoing a longstanding call by many among the Greek left for the group to be banned. Golden Dawn’s opponents may very well now have the political capital they need to bring it to heel.

Meanwhile, fans of Killah P posted this tribute video on YouTube:

[youtube=http://www.youtube.com/watch?v=qUVGzyrUmgA]