People were attacking each other with spears and machetes during a "violent disturbance" on Groote Eylandt on Friday that left two people dead and a third seriously injured, police say.

Police have sent extra officers to the island, including crime scene examiners and five detectives amid fears of revenge attacks in the wake of Friday's events that involved up to 60 people.

During the incident a number of weapons, including spears and machetes were produced and used by the combatants, police said.

Police Commander Tony Fuller said four officers on the island were unable to contain the fight, which saw two men aged 19 and 29 killed, and reinforcements had been sent.

A third person who was injured was in a stable condition at the Royal Darwin Hospital on Saturday, he said.

Commander Fuller was concerned about the possibility of revenge attacks and said the mood in the town was "volatile".

He praised those in the community who tried to quell the violence after the unnecessary tragedy, and local health staff who treated the injured.

Police forced to retreat due to 'overwhelming numbers'

Police said the dispute began after two women had an altercation at the community of Angurugu on Groote Eylandt on Thursday and a male relative intervened.

Key points: Two people killed in Friday's riot on Groote Eylandt

Two people killed in Friday's riot on Groote Eylandt People attacked each other using spears and machetes

People attacked each other using spears and machetes Up to 60 people involved in riot

Up to 60 people involved in riot Police sending reinforcements to Groote Eylandt

Commander Fuller said as a result of that incident a woman was knocked unconscious and taken to the local health clinic.

"On Friday, another male relative has driven from Umbakumba community to Angurugu to find out what had occurred the previous day," Commander Fuller said.

"On entering the community three males threw rocks at his vehicle causing him to crash into a fence.

"This male exited his vehicle with some weapons and began searching for the three males who fled from the area."

NT Police Commander Tony Fuller says up to 60 people were involved in the disturbance. ( ABC News: Jacqueline Breen )

After that incident three men returned with weapons and began arguing with the driver.

"Additional police attended however a large crowd started to gather carrying a variety of weapons including spears," Commander Fuller said.

He said police tried to disperse the crowd but were forced to retreat due to the "overwhelming numbers" of armed people who had gathered at each end of the street brandishing spears at each other.

"One of the group has thrown a spear which has in turn led to an exchange of spears between the two groups," he said.

Commander Fuller said police saw one of the victims being struck, and immediately gave him first aid, but he later died.

"Police also located two more injured persons and evacuated them directly to the clinic," Commander Fuller said.

"Unfortunately, one of the males subsequently passed away as well," he said.

Local highlights ongoing clan conflict

A Groote Eylandt local told the ABC the riot was a result of an ongoing feud between Aboriginal people from the Mamrika and Amagula clans.

The person, who did not want to be publicly quoted on the issue, said unease between the clans goes back decades, possibly hundreds of years, and has led to occasional outbreaks of violence.

They said changes to the traditional locations where people lived, due to a large manganese mine, had forced the clans to live in close proximity, exacerbating the problems.

Chief executive of the Anindilyakwa Land Council, Mark Hewitt, said there was no easy solution to the conflict.

"The reasons for this are complex and multi-dimensional and need to be solved through careful consultation with all clans being in a crowded urban setting," Mr Hewitt said.

Groote Eylandt is Australia's fourth largest island and its economy is dominated by the manganese mine, which produces about one quarter of the world's supply of the metal.

A spokeswoman for South32, which runs the mine, said it was "business as usual" at the mine site, and no workers had been caught up in the rioting.