Authorities have arrested four suspected Greek militants after seizing weapons, ammunition, and computer hard-drives from suspected safe houses in Athens, according to AP. The four men were arrested during the raids late Thursday, and have been charged with participation in an arson attack last year, based on outstanding arrest warrants. Police said Friday they discovered a handgun, an automatic rifle, along with 220 bullets. Attacks by militant groups escalated into deadly violence following massive riots in 2008 over the police's fatal shooting of a teenage boy. On Monday, suspected members of armed anarchist group Conspiracy Nuclei of Fire go on trial on terrorism charges. The group is linked to a spate of parcel bombings in November.