The musician was an anti-fascism rapper and killed by a supporter of neo-nazi group “Golden Dawn”.
Marches were held in his honour, but turned violent as Greek police found themselves in skirmishes at protesters in Piraeus and Thesssaloniki on Saturday.
A group of unknown individuals threw petrol bombs and stones against a riot police van in Piraeus stationed next to the Municipal Theatre, to block access to the offices of Golden Dawn.
There were similar clashes in Thessaloniki.
A group of masked youths attacked riot officers with petrol bombs as they were guarding ruling SYRIZA’s offices.
Violent clashes broke out on Saturday after dozens of hooded demonstrators broke off from a march of 2,000 people marching towards the Golden Dawn offices in central Athens.
Protesters shouted, “Pavlos is alive! Crush the Nazis!”, while holding up banners demanding the party’s offices are shut down and its members are jailed.
Police buses and officers blocked the column from reaching the building.
A group broke off from the demonstration and some threw molotov cocktails.
The police then responded with tear gas.
Most of the marchers dispersed, but a small group continued to throw more missiles outside police headquarters, three were detained.
The murder of Fyssas, whose stage name was Killah P, cause shockwaves among the Greek left-wing community.
It also sparked weeks of protest and disorder.
Giorgos Roupakias was a Golden Dawn supporter and admitted stabbing Fyssas to death, but the case is yet to go to trial.
Nikolaos Michaloliakos, Golden Dawn’s leader, admitted his party holds “political responsibility” for the killing, but he is not criminally liable.
Some people allege the murder was carried out with the knowledge of senior party officials.