Black Sabbath bassist Geezer Butler has recalled the time a "lunatic" threatened to "sacrifice" guitarist Tony Iommi at their Nashville concert.

The heavy metal band - which was fronted by Ozzy Osbourne at the time - were known for their satanic imagery, which didn't go down well with Geezer's "strict Catholic" father, and some Americans.

In an interview with Reader's Digest, he recalled: "My dad wasn’t very pleased when he saw the inverted cross on the sleeve of our first album. But, generally, nobody in the UK or Europe cared that much about our Satanic imagery.

"In the US, though, people would threaten us and turn up at our gigs with crosses and bibles. In Nashville, someone jumped on stage and went for Tony with a knife. Fortunately, Tony had turned around to kick his faulty amp at that point, saw the attacker and got out of the way.

"The police arrested the attacker, though we don’t know what happened to him. But he wanted to sacrifice Tony. Lunatic."

His religious upbringing didn't stop Geezer - who has just released his tell-all memoir 'Into the Void: From Birth to Black Sabbath – and Beyond' - from crossing over to the dark side.

He shared: "I was ultra-religious. It wasn’t surprising as my dad and mum, Mary, were strict Catholics and our house was covered in pictures of Jesus and Mary.

"At school, the nuns would tell us we were going to hell, if we didn’t behave. Terrifying.

"But when I was a teenager, I got into the occult. Magazines, horror films with Vincent Price and books like The Devil Rides Out by Dennis Wheatley.

"There were lots of immigrants with different religions coming into Birmingham, too—Muslims and Hindus. It was fascinating to see new perspectives."