Detectives at Stonnington Crime Investigation Unit continue to investigate an armed robbery where $700,000 worth of jewellery was stolen in South Yarra earlier this month.

Investigators have been told two men were sitting in their vehicle on Avoca Street when two men approached the car and smashed the window just after midday on Tuesday, 14 July.

The pair stole two back packs containing white gold and diamonds from the back seat of the vehicle.

The offenders, both wearing black balaclavas, then fled the scene in a blue Ford sedan and were seen travelling north on Murphy Street.

Detectives believe that another car, possibly a Mitsubishi Verada wagon, followed the Ford sedan to Lawson Grove, South Yarra.

The cars pulled over and three offenders from the Ford got out of their car and got into the wagon which then drove off.

Investigators have released images of the second car in an attempt to identify it.

They have also released images of a man who was seen near a jewellery store on Toorak Road on 14 July who they believe may be able to assist with their investigation.

Detectives also wish to speak to anyone who may have recently sold a blue Mitsubishi Verada, 1999-2000 model, on Gumtree or eBay.