CHICAGO (AFP) - A Ku Klux Klan leader convicted in the infamous killings of three civil rights workers memorialised in the film Mississippi Burning, has died in prison, officials said on Friday (Jan 12).

Edgar Ray Killen was serving a 60-year prison sentence for spearheading the 1964 slayings of the men who were in the southern US state as part of a drive to register black voters.

The case galvanised public opinion against segregation and helped lead to the passage of the Civil Rights Act. It also inspired the Oscar-winning 1988 film Mississippi Burning.

Officials said the 92-year-old Killen died late on Thursday.

"The cause and manner of death are pending an autopsy. However, no foul play is suspected," the Mississippi Department of Corrections said in a statement.

Killen was accused of orchestrating the shocking murders of the three political workers - two white men and one black man.

James Chaney, Andrew Goodman and Michael Schwerner initially went missing after being arrested by local police and then released.

The sheriff's deputy who arrested them informed Klansmen of their detainment, and Killen then orchestrated a KKK mob to attack the men.

The three men were initially considered missing, and the FBI joined in the search to find them.

Weeks later, their buried bodies were discovered at a farm, shot at point-blank range. Chaney, the only African American among them, had been badly beaten.

Killen had escaped punishment for almost four decades, his initial trial ending in a hung jury.

He had been living as a part-time preacher and lumber mill operator, but was also an organiser in the KKK who had established a local group.

The case was reopened in 2005, and Killen was convicted and sent to prison. He was the only one of the culprits to be convicted of murder charges.