* Anti-fascism rallies planned in Athens and Thessaloniki
* Poll shows Golden Dawn losing support
* Killing led to crackdown on party
Greeks staged protests in Athens on Wednesday against the fatal stabbing of an anti-racism rapper by a supporter of the far-right Golden Dawn party, which a new poll found has lost a third of its support since the killing.
The death of 34-year-old Pavlos Fissas has fired outrage across the political spectrum against a party that is widely regarded as neo-Nazi and whose popularity has so far appeared immune to accusations of brutality and violence.
Golden Dawn denies the neo-Nazi label and any involvement in the attack, saying it is the target of a witch-hunt after the government began efforts to crack down on the party and its alleged influence over the Greek police force.
Anti-fascist rallies planned to coincide with a 48-hour public sector strike on Wednesday have overshadowed anger over layoffs demanded by EU/IMF lenders.
Hundreds of people began gathering in the central Syntagma square for a memorial concert by hip hop groups, some holding banners saying "Fascists out of neighbourhood".
"The crisis brought us to our knees but we need to say a loud 'no' to fascism like we did in '74," said Vangelis Georgountzos, 59, referring to the student uprising that led to the overthrow of Greece's then-ruling military junta.
Standing in the crowd that flooded the street in front of parliament alongside his teenage daughter, Georgountzos said: "First it was the immigrants, then Fissas, tomorrow it could be your son or daughter - everyone needs to understand this."
Marches by university students, labour unions and leftists are expected to culminate later in an anti-fascism demonstration outside parliament, the scene of often violent anti-governmemt protests in the past. Rallies were also planned in Thessaloniki,
Greece's second-biggest city.
"The heinous and cowardly murder of anti-fascist Pavlos Fissas has revealed ... that Golden Dawn is the enemy of democracy," public sector union ADEDY said.
Local radio played an anti-fascist anthem against Greece's Nazi occupation during World War Two.
Mourners had laid flowers and candles at the spot in the working-class neighborhood of Keratsini where Fissas, who performed anti-racism raps under the stagename Killah P, was stabbed,
"Murderers!" declared a banner above the makeshift shrine, while a slogan scrawled on the shuttered window of a nearby shop read "Crush the fascists!".
"CLIMATE OF TERROR"
Golden Dawn is Greece's third most popular party and the most visible symptom of discontent over state corruption and a deep economic crisis that has fuelled hostility to immigrants.
But polls since Fissas' killing show support for the party has fallen rapidly. An ALCO survey for the Newsit.gr website, conducted in the days after the stabbing, found support for the party fell by 4 percentage points to 6.8 percent.
Nearly 80 percent of Greeks said such violent acts were a threat to democracy.
"Golden Dawn voters haven't changed their minds, they're simply not saying who they'll vote for because of the current climate of terror," the party responded in a statement.
The party says petrol bombers have attacked its offices in recent days and that assailants smashed the window of an animal food shop in central Greece belonging to one of its lawmakers.
Golden Dawn, once a fringe party, won 18 seats in parliament in elections last year and has since gained support among Greeks struggling to make ends meet by organising frequent "Greeks-only" food handouts.
Rights' groups have long linked Golden Dawn supporters, dressed in black and often seen giving Nazi-style salutes, to violent attacks on immigrants, something the party denies.
Fissas's killing has led to an investigation into the party for evidence linking it to the attack. It has also prompted an unprecedented shake-up of Greek police following reports that Golden Dawn party cells were operating within the force.
That has raised questions about whether the government will seek to ban the party altogether, though the public order minister has said this would require constitutional changes that could take years.
"Part of society, disappointed by the errors of the traditional political system, silently accepted practices that threaten democracy," the union representing Greek telecom employees said. "Enough is enough."