More (n greek) http://athens.indymedia.org/front.php3?lang=el&article_id=919612:
From the mass-media: Minor material damages were caused to the entrance of ROUF military courthouse at 2:35 in the night, after a combustion of an improvised incendiary device made of 10 home gas canisters. According to the first information, a fire erupted followed by an explosion breaking the entrances' glass windows. A little after 7:00 a.m. the police found near the barracks' entrance a hole in the fencing wire where the penetrators allegedly entered from. It is worth noticing that the arsonists weren't noticed, since the area is guarded by the army.
Update: According to "Eleftherotipia" newspaper(http://www.enet.gr/online/online_text/c=112,id=75353488), the «Conspiracy of Cells of Fire - Revolutionary Army cells» claimed with a phne call to "Eleftherotipia" the responsibility for the attack "in solidarity to Giannis Dimitrakis, who was facing a military jury on October 13".