One person has died following Tuesday afternoon's suspected stabbing in central Whanganui.
Police have launched a homicide investigation after the incident in Wicksteed Street, detective inspector Paul Baskett said.
Five people were taken to Whanganui hospital with moderate to serious injuries while a sixth person has died at the scene which police were called to at about 4.15pm.
"The investigation is in its very early stages, however we can confirm that one person was taken into custody immediately after the incident," Baskett said.
Police are not looking for anyone else in relation to this matter.
Cordons are in place on Wicksteed and Liverpool streets and will be in place overnight.
A worker from medical centre Te Oranganui, who did not want to be named, said a colleague witnessed the stabbings.
Te Oranganui nurses and a doctor ran to the aid of the victims.
"When I got there, there was one lying on the ground. It was a big girl. She'd been stabbed, it was bad."
The worker said two other people who had been stabbed were walking around
"You could see it. He was holding his neck and blood was pouring out. On his back, you could see where he'd been cut.
"There was another lying down, she wasn't moving. She was an older lady."
The worker believed the stabbing victims were four members of one family.
Police had cordoned off a house in Wicksteed St and were also carrying out investigations there.
There were three upturned supermarket trolleys within the carpark cordon.
Another witness told Stuff he was putting groceries into his car when he heard cries for help.
"She had severe facial and arm lacerations, and told us she and others were attacked by a man with a knife on the corner of Wicksteed and Liverpool streets."
He helped comfort her until emergency services arrived.
During that time another man approached from Liverpool St with a stab wound to his neck and told those gathered there was another woman who was badly injured.
Police are not yet in a position to release the name of the deceased.