Four masked robbers armed with automatic rifles and pistols barged into a branch of Piraeus Bank on Kifissias Avenue in the Ambelokipi district of Athens on Tuesday and held employees and customers hostage for two hours before making a getaway.
Unconfirmed reports said they stole more than 60,000 euros after forcing the manager to open the bank safe at gunpoint.
They also used drills and welding devices to open up more than 20 deposit boxes.
Police were alerted after the robbery ended.
Witnesses said the robbers left the bank on foot and got into getaway cars a short distance away, driven by accomplices.