Police are hunting a bandit who held up a Geelong petrol station at knifepoint during the night.

The man went into the Apco service station in Thomsons Road at around 10.25 last night and threatened the attendant.

He ran off after being given an unspecified amount of cash.

A large search by the police helicopter and ground patrols failed to find the man.

Police say the suspect was wearing a hoody and a cap, and had a scarf over his mouth.

The service station staffer is reportedly shaken but unharmed.

Anyone who saw something suspicious or who may know something about the robbery is asked to call Crime Stoppers on 1 800 333 000 or visit the website at www.crimestoppers.com.au.