Detectives are investigating the armed robbery of a business in Salisbury yesterday afternoon.

Initial enquiries indicate at about 3pm, four men approached a post office on Ainsworth Street. While two men waited outside, the other two entered the store and one man threatened the attendant with a knife.

The other man then assisted him to take a sum of cash from the register, before leaving the scene on-foot toward Birchdale Street with the other two men.

Nobody sustained any physical injuries during this incident.

It is believed all four men were wearing hooded-jumpers and long pants at the time.

Police are appealing for any further information from the public in relation to this armed robbery.