Logan detectives are investigating two linked armed robberies overnight in which service stations were held up by a man with a firearm.

Around 9pm, a man entered a Henry Hester Drive, Stapylton, store and threatened the 31-year-old male attendant before fleeing with a sum of cash from the till and cigarettes.

Shortly after 10pm, a man entered a Logan Road, Underwood, store and threatened the 63-year-old male attendant with a firearm before pushing him to the ground.

The man again threatened the attendant before fleeing with a sum of cash from the till and cigarettes. The attendant did not require any medical treatment after the incident.

During both incidents, the offender was described as Aboriginal or Torres Strait Islander in appearance, between 175 and 180cms tall, with a proportionate build and dark hair.