Christchurch police are warning Shirley residents not to be alarmed if they see armed police running around a local abandoned high school.

Police will be conducting a training exercise at the old Shirley Boy's High School grounds on North Parade this week.

A spokesperson says they conduct this type of tactical training regularly, to make sure officers get to practice live incident responses.

They say people may hear glass breaking and loud bangs and will see a lot more police in the area.

Police will use “three air horn blasts” to warn the public before any explosives are detonated.