Police investigating the theft of 15 assault rifles in Northland are warning gun collectors to be alert for suspicious phone calls.
They say several collectors have had calls that appeared to be an attempt to find out whether or not they are home.
They want to hear from gun holders in Northland and Auckland who have had a similar experience, including calls in which the caller hangs up without speaking.
Detective Inspector Kevin Burke said police were investigating whether the phone calls were linked to the theft of weapons from a Dargaville collector last month.
He is asking anyone with firearms to make sure their guns are stored securely, and for retailers to report anyone asking for ammunition for AK-47 and AK-74 weapons.