Twitter has permanently banned white nationalist David Duke for repeatedly violating its rules about "hateful conduct".

The social network changed its policy in March and no longer lets people share links to articles that include "hateful content" or incite violence.

The Anti-Defamation League (ADL), an anti-hate organisation, describes Duke as "perhaps America's most well-known racist and anti-Semite".

He was banned from YouTube in June.

Duke's final tweet linked to an interview he had conducted with Germar Rudolf, who was convicted of Holocaust denial in Germany where it is a criminal offence.

His penultimate tweet promised to expose the "systemic racism lie", while another claimed to expose the "incitement of violence against white people" by Jewish-owned media.

Duke founded the Knights of the Ku Klux Klan in the 1970s.

He pleaded guilty to tax fraud in 2002 and spent a year in a US prison.