Detectives are investigating two robbery incidents overnight in which a firearm was used to threaten restaurant staff at Yandina and the Glass House Mountains.

Around 6.30pm, a man entered a Ninderry Road restaurant at Yandina and threatened a staff member with a firearm before fleeing with money from a register.

The man is described as Caucasian in appearance, approximately 180cms tall, with brown eyes and dark facial hair.

At the time, the man was wearing a blue long sleeve work shirt with two yellow high visibility panels on the shoulder and front, shorts, work boots and red cloth coverings across his face.

Around 10.20pm, another, attempted, robbery took place at a restaurant on Steve Irwin Way at the Glass House Mountains in which the offender fled empty handed.

At that time a man bearing a firearm threatened a female employee, before the woman fled to another room.

The man then left the scene in a nearby vehicle.

No one was injured during either incident.