Two men have died and three are critically injured after a huge brawl in Gisborne overnight.

About 100 people were involved in a massive fight on Lytton Road in Elgin, police said.

Officers arrived about 11.30pm Saturday.

"A number of police units were needed to gain control of the scene, and during this time two men were located deceased," acting inspector Danny Kirk said.

"Three others have been transported to hospital in a critical condition."

A woman who lives on the Gisborne street where the brawl took place described it as a gang area.

The resident, who asked to be anonymous, said she heard yelling and fighting breaking out at what was otherwise a quiet party about 11.30pm on Saturday.

She came home from work to the quiet party across the street, she said.

"It would've been just after 10.40[pm] when we got home and I happened to see a Mongrel Mob coming up.

"It was actually a quiet party. Yeah, it was just a party. I didn't even know that anything was gonna happen."

She said she did not feel safe living in the area today.

"We are in the middle of Black Powers and Mongrel Mobs, so Black Power do actually live really close, so it is a gang-related sort of thing.

"I can go to work, because there is a back way to go to work, but I refuse, just for my own safety."

The resident said she saw gang members at the party, before hearing a fight break out later on.

"All I heard was just swearing, yelling, and I heard the pops as well. My partner was telling me, oh there's a lot of pops and cops coming. ... [we] didn't realise it was that close to home."

The woman said police cordons were still in place outside her house, and she had been told roads were closed until Monday.

Homicide investigation launched

Meanwhile, a Gisborne Hospital spokesperson confirmed to RNZ the hospital is in lockdown. It is unclear if this is related to Saturday night's incident.

Police have launched a homicide inquiry after the deaths.

"Cordons remain in place and a scene examination will be carried out this morning," Kirk said.

"We know that events like this are incredibly concerning for our community. Police will have a highly visible presence across Gisborne over the coming days, and extra patrols will be carried out to provide reassurance to members of the community."

Additional police staff had been called on to assist, he said.

Further information would be released when it became available.

Mayor says brawl could be party gone wrong

Gisborne Mayor Rehette Stoltz said the news was "heartbreaking".

"It's heartbreaking for our community and it's heartbreaking for the families of the men involved."

Mass brawls had not been an ongoing problem in Gisborne, she said.

"I know that our community will feel this. It doesn't matter what happened, families are affected and there are families mourning this morning.

"Our thoughts are with them and our thoughts are also with our police who have to deal with this and keep our community safe."

Stoltz said she had spoken to police on Sunday morning.

"The update I got is that they want to reassure the community and them having more visible police around will give that reassurance to the community in this tough time."

She said she had heard the brawl was a party gone wrong.

"A state of shock and disbelief" - East Coast MP

East Coast MP Dana Kirkpatrick said the brawl would be shocking to the community.

It was an incredibly upsetting event for the community and for families affected, and she would be speaking to the mayor and the Police Minister later today.

"The community will be in a state of shock and disbelief.

"We pride ourselves on our town and so clearly, there's been an incident that the police will be dealing with.

"We should handle this with care, and we should also let the police get about their job and [undertake] the investigations they need to bring this to a close."

Police Minister Mark Mitchell is on his way to Gisborne and will be meeting with the mayor this afternoon