A man who allegedly used a gun to holdup an Aldi supermarket in Melbourne's south-east has been on the run for almost two years.

Police are today calling for the public's help to track him down, having released photos and CCTV footage of him moments before the robbery.

The man loitered around in supermarket on Frankston-Dandenong Road in Carrum Downs before he exited the store about 12.30pm on Tuesday, September 15, 2020.

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He was then outside the store when he approached a staff member while allegedly holding a gun.

The man handed the staff member a bag and demanded the worker fill it with cash.

He then followed the worker to the cash register, where the worker filled the bag with money.

The man when ran from the store with the cash.

No one was injured.

The man was perceived to be Caucasian in appearance, aged in his 20s and was wearing a black face mask and orange high vis top.

Anyone with information or any witnesses are urged to contact police.