Police are investigating the armed robbery of an Inala service station last night.

Preliminary information suggests around 11.30pm, two men entered the Rosemary Street store armed with a knife.

The men fled the scene with a sum of cash.

A male staff member was able to secure himself in a back room of the business and was not physically injured.

The men are both described as around 18 to 20 years old, Aboriginal and Torres Strait Islander in appearance, around 180cm tall and of a proportionate build,

The first man was wearing a dark-coloured Converse-branded hooded jumper and beige pants.

The second man was wearing a grey hooded jumper, dark pants and a mask over his face.