A road rage incident involving crowbars and other weapons on Prebensen Drive, Napier, left one man with a broken arm and facial injuries.
Police are hunting for the occupants of several cars they say had earlier taken off in pursuit of the victim's vehicle.
"We are still not entirely sure at this stage what has sparked it," Detective John McGregor of the Napier CIB said of Sunday's incident.
Detectives had spoken to the injured driver, a 54-year-old local man, and his passenger who was not seriously injured during the incident, but were still working to establish a motive for the attack.
It began about 2.20pm on Church Rd in Taradale when up to five cars started pursuing the man's white Toyota station wagon.
"It is very alarming to have something like this happen in the middle of the day," ' Mr McGregor said.
The pursuit ended a short time later on Prebensen Drive between the entrance to Park Island and the roundabout turn-off on to SH5.
One of the chasing cars got in front of the Toyota and struck its front, while another vehicle rammed into the back.
Several occupants then got out and took to the driver with what police described as "crowbars and other weapons".
The attack was witnessed by several other stunned drivers who came across the scene.
"We have spoken to about four people so far who witnessed it but there were others in that area and we would like to hear from them."
One in particular police want to hear from is a woman who stopped and briefly spoke to an officer at the scene.
The driver was taken to Hawke's Bay Hospital for treatment, but was released later in the day.
The passenger was not badly injured as the group appeared more intent on attacking the driver.
"We need to speak to anyone who saw the incident or any witnesses who may have seen the vehicles chasing the Toyota in the Church Rd, Park Island and Prebensen Dr areas," Detective Mike Signal said.
"There was a reasonable amount of traffic on the roads at that time on Sunday and it's important we speak with anyone who saw any vehicles speeding or appearing to race in the area."
Anyone who witnessed the incident can call Napier Police on 831 0700 or use the anonymous Crimestoppers line 0800 555 111.