Greek Finance Minister Yannis Stournaras received a bullet in the post, Greek media reported on Monday.

Stournaras' aides alerted security forces, when they opened the envelope at his office and discovered the enclosed bullet. According to media reports, the envelope also included a threatening letter signed by "The Cretan Revolution."

Perpetrators warn the official "not to sell off Greek soil," in a reference to the ongoing privatization program introduced in the context of wider austerity and reform efforts to resolve the Greek debt crisis.

In January this year, the headquarters of the ruling party came under attack with Kalashnikov assault rifles and a major shopping mall and other political and media targets were firebombed in political motivated violence.

Monday's incident came as counter-terrorism squads were investigating a terrorism hideout in Athens discovered after the arrest of suspect members of the "Conspiracy of Fire Nuclei" among a group of alleged bank robbers apprehended last Friday in northern Greece.

According to police statement, heavy weaponry was found in the apartment.

"Conspiracy of Fire Nuclei" has been linked to a series of attacks against political, police and business targets in recent years.

Earlier on Monday, prosecutors in Athens opened a probe into allegations that the four suspects aged 20 to 24 arrested for a double bank robbery in a northern Greece city on Friday were mishandled by police.

Greek police officials reject the claims, stressing that any injuries occured during the operation to disarm and detain the robbers who were armed with Kalashnikov rifles and handguns.