Armed police have been watching over the scene of a suspicious fire in Whau Valley, Whangarei.

There've been three serious house fires in Northland over the course of just 36 hours.

Armed officers were at the Whau Valley address yesterday after the property was destroyed in a blaze on Thursday.

Northland police media spokeswoman Sarah Kennett says armed officer aren't usually necessary at the scene of an arson attack.

However, no further comment could be made at this stage.