The driver of a red Holden Barina allegedly produced a firearm while driving northbound on the Monaro Highway, Hume, at around 12.50pm on Wednesday, police report.

The male driver is described as Caucasian in appearance, believed to be in his late 20s, with a blond mullet-style haircut and has facial scarring.

Police are looking for witnesses or anyone with dashcam footage of the Barina driving around Hume to provide their contact details via the  Crime Stoppers ACT website.