Authorities say they believe the heists have given the guerrilla bands cash reserves more than adequate to supply them with explosives and firearms.
The culprits are believed to have been spawned by the notorious Revolutionary Struggle and November 17 groups, which were largely dismantled by 2002.
Nikos Maziotis, the convicted leader of Revolutionary Struggle, dropped out of sight in 2012 and is believed to have taken part in at least five bank heists since then, police sources told ekathimerini.com Sunday.
Also at large was Christodoulos Xeros, who skipped out on his parole this month and had been in regular contact with other militants during his time in prison.
Greek authorities, in an effort to head off a potential major terrorist attack in Greece, have been looking into the bank accounts of individuals tied to the guerrillas.