Two white South Africans accused of forcing a black man into a coffin and threatening to set him on fire have been convicted of attempted murder, kidnapping and other charges.

A judge on Friday delivered the verdict in Middelburg in Mpumalanga province in a case that prompted national outrage and debate over the legacy of white minority rule, which ended in 1994.

A video showing the racially charged incident circulated on social media last year, leading to the arrest of farmers Willem Oosthuizen and Theo Jackson.

It shows a man cowering and moaning in a coffin as part of the lid is pushed over his head and upper body. A man is heard threatening to pour in gasoline. Another threat is made to put a snake in the coffin.