Port Philip Crime Investigation Unit detectives are investigating following an armed robbery at a food store in St Kilda East yesterday afternoon.

Investigators believe a man attended the Westbury Street store at about 3.30pm yesterday and demanded cigarettes.

The man produced a large kitchen knife from his backpack.

Cigarettes were stolen and the male fled on foot along Alma Road where he got into a black hatchback – possibly a Mitsubishi or VW.

The man is described as about 30-years-old with tanned skin, a thin build and wearing a yellow fluorescent top with long black sleeves, khaki tradie-style shorts and dark coloured gloves.

He was wearing a black balaclava.