A pregnant Queensland woman was allegedly threatened at gunpoint while trying to stop a robbery overnight.

The incident occurred at around 9pm in a suburb north of Brisbane.

It's believed the 18-year-old woman saw the thief take a motorbike from a car park at a unit complex and decided to follow him in her car.

View photos A man stole a motorcycle and threatened a woman with a firearm in Deception Bay last night according to police. Source: 7 News. More

View photos A search for the man involved is underway. Source: 7 News. More

During the pursuit she crashed her car and the thief then allegedly threatened her with a gun before running off.

The woman wasn't hurt during the incident.

View photos Police report the man stole a motorcycle from the communal car park. Source: 7 News. More

View photos The woman was not physically injured as a result of the incident. Source: 7 News. More

A widespread police manhunt to locate the man is currently underway.