A man has been shot dead in Whanganui.

Detective Inspector Ross McKay said police have started a homicide investigation in Whanganui after a fatal shooting incident in Puriri Street, Castlecliff, this morning about 9.40am.

The offenders remain outstanding, however it was believed those involved were known to each other and were known to police, he said.

McKay said additional staff have been sent to Whanganui to assist.

Police are at a property in Puriri St and the road is cordoned off between Rogers St and Kowhai St. An ambulance was also called to the property.

A resident said he heard three gun shots and said he saw gang members running from the scene.

Another resident said she heard two gun shots.

Police confirmed an incident was reported at 9.42am and had led to part of the street being closed.

"Parts of Puriri St have been closed and the public are asked to avoid the area," a spokeswoman said.

It is understood a school in Matipo St has been put into lockdown. The school was not answering phone calls this morning.