A person is in a critical condition in Wellington Hospital after being assaulted in Whanganui on Thursday evening.
Whanganui Field Crime Manager Inspector Paul Baskett said in a statement the incident happened at about 5pm on Moana/Duncan Street.
An arrest has not yet been made and police are appealing for information from the public to assist their investigation.
"Anyone that has electronic recordings, CCTV or witnessed the incident is encouraged to speak with police so we can piece together what happened," Baskett said.
"If you live nearby, have a look around your property and if there are any discarded objects in the area, report to police straight away.
"It is important that if you know who is responsible for this attack that you come forward and tell police what you know," he said.
A scene guard was in place overnight and a scene examination was conducted by the Criminal Investigation Branch (CIB) on Friday morning.
Baskett said Fire and Emergency NZ also attended in order to assist police in clearing the scene.
Information can be provided to police by calling 105 and quote file number 220512/6199. Alternatively, information can be given to Crime Stoppers anonymously on 0800 555 111.