An investigation is underway after an armed robbery in Sydney’s west.

Police were called to a fast food store on Chester Hill Road, about 9.30pm yesterday (Wednesday 23 May 2018), following reports man, armed with a firearm, entered the store.

The man threatened a staff member and demanded cash, before leaving the scene.

Officers attached to Bankstown Police Area Command attended and conducted a canvass of the area, with assistance from the Dog Unit, before establishing a crime scene.

The man is described as being about 188cm tall with a medium build. He was wearing a blue hooded jacket with white writing, dark blue pants and black shoes.

Inquiries are continuing.