The Elliot post ioffice was robbed by three men - one posing as a police official - at 4.30pm on Monday.
According to police spokesperson Captain Ursula Roelofse, the three robbers approached the two security guards on entering the post office.
“One introduced himself as a police detective and shook the hand of the guard who was carrying a firearm. While shaking his hand, one of the other suspects grabbed the security guard's firearm and instructed them to go into the manager's office," she said.
"They also forced the three clients who were being served at the post office, into the s office.”
Roelofse said the guards, clients and all the cashiers - except one - were then tied up with cable ties.
“The cashier was told to take out all the money and put it in a bag. The suspects then took off with an undisclosed amount of money."
No shots were fired during the robbery.
A case of armed robbery is under investigation.