Police said in a statement that the man threatened staff and made demands about 11am Saturday.

"The staff member complied, handing over a sum of cash and cigarettes. The man was seen getting into a white Holden Commodore with ACT registration," police said.

"The alleged offender is described as Caucasian in appearance, aged in his early 20s, between 178cm (5’10”) and 183cm (6’) tall, with a slim build and short black hair."

He was wearing a black T-shirt and jeans, with black canvas tennis shoes and a black scarf over his face at the time, and was seen carrying a green enviro shopping bag.

"A person matching this description had been seen at Higgins Shops earlier this morning," police said.

"Police would like to speak with any witnesses from Holt and Higgins Shops who they have not yet spoken with."

They ask anyone who might be help their investigation to contact Crime Stoppers on 1800 333 000 or at www.act.crimestoppers.com.au.