"The armed robbers had hidden inside the post office. They jumped out at the staff on their arrival and forced them to open up the vault," a policewoman told AFP.
Some 50,000 euros in cash and 20,000 euros in tax stamps were stolen by the thieves, who fled back along the 12-metre (39 foot) long tunnel which they are believed to have dug during the weekend, she said.
Before making their escape, the bandits -- dressed entirely in black -- locked the 12 members of staff in the vault. Their toy guns were later discovered discarded in the tunnel.