Authorities in the US are on high alert after they were warned a prison gang was "going to kill correctional officers" during August in a revenge attack for the death of one of its members.

The Black Guerrilla Family (BGF) prison gang, which originated in California, has long participated in so-called 'Black August', a month of increased violence to honour fallen members – and US police has warned this month could see more violence than usual.

In a bulletin sent to law enforcement and prison guards, it was warned that attacks in prisons and on the streets could see an escalation of violence after a member of BGF was stabbed to death during a prison riot in Sacramento last year – in what the gang believes was an attack orchestrated by police and members of the Aryan Brotherhood gang.

An extract from the bulletin published by abc7 states a source: "Claims the BGF has a 2-for-1 kill policy."

It added the gang was "going to kill correctional officers and Aryan Brotherhood gang members to send a firm message. And the attacks will occur across the country, not just in California, and will likely occur during the BGF's memorial celebration of Black August."

The gang member who was killed in the prison riot in Sacramento in 2015, Hugo Pinell, had been in solitary confinement for 46 years after originally being incarcerated for a rape and subsequently killing a prison guard and seriously injuring two others when he tried to escape in 1971.

After he was released from solitary confinement he was stabbed to death less than two weeks later during the riot – and the gang believes prison guards conspired with the Aryan Brotherhood to organise the killing.

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