Police are investigating an aggravated robbery that occurred yesterday at Parafield Gardens.

Just after 6.10pm a 28-year-old man was leaving his store, an Asian supermarket on Martins Road when he was approached by a man armed with a syringe.

An altercation took place and the victim was punched.

The suspect stole a shopping basket and an amount of cash before fleeing on a bicycle which was possibly silver in colour

He was last seen heading towards Shepherdson Road.

The victim sustained minor injuries during the incident and was treated at the scene.

The suspect is a man of Caucasian appearance, 25 to 28 years of age, about 165 to 170cm tall, of slim build, with short fair hair.

He was wearing dark pants and a dark hooded jacket.

Police ask anyone who witnessed this incident or with any information to contact BankSA Crime Stoppers on 1800 333 000 or online at www.sa.crimestoppers.com.au