Warning: Graphic Content

An eye witness has described the "shocking" attack of a man by two patched gang members on the main street of a Waikato town as families looked on.

A man in his 30s died following the attack shortly after 6pm on Saturday in Ōtorohanga and police have launched a homicide investigation.

The witness said he was driving down Maniapoto St and pulled over as he noticed a fight unfolding outside the Mobil service station.

"I was just driving down and there was a scuffle. It's a pretty quiet town too which really sucks but there was a scuffle so I kind of slowed down," the witness said.

"It was these two gang members and they were attacking this [man] ... they hit him on the head and it just dropped him cold and they just took off. Pretty shocking really."

The witness told the Herald that the gang members fled in a white Rodeo ute.

A friend of the victim was also on the scene as the man in his 30s was attacked.

"He was with his mate, he had a motocross bike on the back [of their vehicle], they looked like they had just been out for the weekend sort of thing," the witness said

"He didn't get involved, he stepped back ... they had their patches on and everything. Just your classic sort of thug."

The witness said he then got out of his car to assist the badly injured man who he says was wearing high-vis clothing and didn't look like a gang member.

"I got out and ran back down and there was a young family there and a couple of other people," the witness said.

"I stopped actually and tried to get that guy on his side. Get him in the recovery position," the witness said.

"There was a fair bit of blood [but] it actually didn't look that bad. I sort of thought he'd bounce back.

"I thought he was knocked out, I thought he'd come back."

Police were called to Maniapoto St around 6:30pm to reports of a large group of people fighting.

Police inspector Neil Faulkner said on arrival, a man in his 30s was located seriously injured.

"Medical attention was given but unfortunately the man died at the scene," Faulkner said.

"Police are following lines of inquiry to locate those responsible. We want to reassure the public police are committed to holding these offenders to account.

"Residents of Ōtorohanga can expect to see a police presence in the town overnight and into tomorrow as we work to determine the circumstances of this incident."

The witness said within about five minutes of the attack numerous carloads of people had turned up who seemed to know the man and were getting very angry.

"There were a few people around and then it all sort of kicked off," the witness said.

"It looked like all his family and all his mates were coming down and they were spewing, they were smashing **** on the ground and yelling and I thought I'm just going to get out of here," the witness said.

"People knew him in the area I think a phone call got put out. Within five minutes like 10 carloads of people had pulled up."

The witness said the incident did not reflect the town of Ōtorohanga.

"It's a really cool town, they just raised $7 million for a dementia unit, all through the community. It sucks it's a really nice town. It's just your classic country town really."

Police said a section of Maniapoto St/SH 3 was cordoned off while officers conducted a scene examination, and was likely to remain so for some time.

A worker at the Pizza Zone restaurant on Maniapoto St said they could not operate because the street has been shut down by emergency services.

"We have no idea. We are not allowed to do business," the staff member said, noting there were a lot of police at the scene. "I just heard an ambulance."

The worker said they had heard from others that someone had died.