Christchurch police are at the scene of an aggravated robbery of a dairy involving a firearm.

A police spokesperson said the incident happened on Wycola Avenue, Hei Hei around 4:05pm.

A man allegedly entered the Wycola Dairy with a firearm and threatened an employee.

He left prior to police arriving at the scene the spokesperson said.

A scene guard is in place and enquiries to locate and identify the offender are ongoing.

Police didn’t release a description of the offender.

It’s understood the offender was wearing a balaclava.