A member of the Greek neo-Nazi group Golden Dawn was arrested Wednesday on suspicion of involvement in the stabbing of anti-fascist hip-hop artist Pavlos Fyssas, BBC News reported.

Clashes broke out near the scene of the crime as anti-fascist demonstrators sparred with the police later Wednesday, according to the Associated Press.

Golden Dawn, a group frequently accused of violence, has denied any association with the Fyssas' death, according to Agence-France Press.

The killing, which came hours before thousands were planning to rally against the government's austerity measures, has added to social instability as debt-strapped Greece adopts unpopular fiscal reforms. Amnesty International has issued an urgent statement calling on athorities to do everything in their power to "prevent further politically motivated violenc."

The nation's Public Order Minister Nikos Dendias said the crime "shows in the clearest possible way the intentions of the neo-Nazi creation," adding, "I am shaken by the event," reported the International Business Times.

The atmosphere in Athens is so tense that Dendias decided not to leave for a planned visit to Rome, said the BBC.

Fyssas, a 34-year-old rapper alternately known as "Killah P," was stabbed to death just after midnight on Wednesday outside a cafe in Keratsini, a western part of Athens.

The anti-fascist artist was assaulted by a group of 15 men, reportedly after an argument over football.

Reporting from Athens, the BBC's Mark Lowen said a 45-year-old Golden Dawn supporter admitted to the killing.

Police also raided the Golden Dawn headquarters in Athens.

Fyssas' death has already sparked memorial videos from many of his fans, such as the following: