The final arrest took place in Somerset East where one of the post office employees was arrested.
All four suspects will appear soon in the Somerset East magistrate's court on charges relating to possession of suspected stolen money and possession of unlicensed firearms and ammunition.
According to StatsSA, there are just over 3,700 households in the small Karoo town of Somerset East.
The Eastern Cape provincial commissioner, Lt Gen Liziwe Ntshinga, commended officers from various units - including those deployed from neighbouring towns - who joined forces to track down the suspects.
"When we co-ordinate our operations, swift results are achieved. These arrests are an indication that police throughout the province are on high alert, even in our rural and semi-urban towns," she said.