The Supreme Court has overturned a ban on a rapid fire gun accessory used in the United States' deadliest mass shooting.

The Court ruled six to three to lift the federal ban on bump stock devices that allow semiautomatic rifles to fire hundreds of bullets a minute.

It was initially introduced by the Trump administration in 2018 - after 60 people were shot at a Las Vegas music festival.

US Correspondent Richard Arnold says critics have labelled this reversal 'dangerous'.

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