From Dawn of the Greeks blog:
They have sprayed a Celtic cross and the a threatening message “we are coming”. Solidarity network of Zografou is a very active group in the suburb, also known for its antifascist actions. Many of its members also take part in the antifascist coordination/front of the area which organized a variety of activities the previous months.
Therefore the neonazis have chosen this place as their target. The autonomous nationalists (independent nationalists) is a group of which its leader Antonis Panoutsopoulos (nickname Periandros) stayed in prison for 4 years accused for an attempted murder of the student and active member of a extra-parliamentary left group Dimitris Kousouris.
More in Greek: http://left.gr/news/o-periandros-xanahtypa.