Brazilian authorities have launched an investigation after gold miners bragged about massacring 10 members of an uncontacted indigenous tribe in the Amazon.

Brazil's agency on indigenous affairs, Funai, filed a complaint with the prosecutor's office in the state of Amazonas after a group of miners were recorded boasting about the killings.

"It was crude bar talk," Leila Silvia Burger Sotto-Maior, a coordinator for uncontacted and newly contacted tribes at Funai, told The New York Times.

"They even bragged about cutting up the bodies and throwing them in the river."

She said the miners claimed "they had to kill or be killed".

The killings are believed to have taken place near the Peruvian border in the Javari Valley, a territory where around 20 of 103 uncontacted tribes in Brazil live.

Another Funai official, Gustavo Souza, who heard the recording, told the Thomson Reuters Foundation the miners spoke of shooting at women and children who were on a riverbank.

He said he had seen a photograph of a hand-crafted paddle, which was reportedly taken from the indigenous group.

Federal prosecutor Pablo Luz de Beltrand confirmed an investigation had been opened after his department received the audio clip, which was recorded by an unidentified person.

It is the second such incident this year. Investigators said they were looking into claims of another killing of uncontacted indigenous people that allegedly happened in February.

Rights groups blamed austerity measures for an increase in attacks.

Brazil's president Michel Temer has overseen deep cuts to funding for indigenous affairs, resulting in Funai closing five of 19 bases used to protect uncontacted communities.

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At the end of August it emerged Mr Temer's government had abolished the protected status of a vast portion of the Amazon rainforest.

Mr Temer is facing a barrage of corruption charges, which he denies, and critics claim he is attempting to win the support of mining lobbies to protect him from being ousted.

Campaign group Survival International said the incident amounted to genocide.

Director Stephen Corry said in a statement: “If these reports are confirmed, President Temer and his government bear a heavy responsibility for this genocidal attack.

"The slashing of Funai’s funds has left dozens of uncontacted tribes defenceless against thousands of invaders – gold miners, ranchers and loggers – who are desperate to steal and ransack their lands.