Michael Clarke Duncan, the prolific character actor whose dozens of films included an Oscar-nominated performance as a death row inmate in The Green Mile, has died aged 54.

Duncan died on Monday at the Cedars-Sinai medical centre in Los Angeles, where he was being treated for a heart attack, according to his fiancee, Omarosa Manigault.

The muscular, 6ft 4in Duncan – a former bodyguard who turned to acting in his 30s – "suffered a myocardial infarction on 13 July and never fully recovered", said a statement issued by a spokesman.

"Manigault is grateful for all of your prayers and asks for privacy at this time. Celebrations of his life, both private and public, will be announced at a later date."

Earlier this year Duncan had appeared in a video for Peta, the animal rights organisation, in which he spoke of how well he felt since becoming a vegetarian three years earlier.

"I cleared out my refrigerator, about $5,000 worth of meat," he said. "I'm a lot healthier than I was when I was eating meat."

Duncan had a handful of minor roles before The Green Mile brought him an Oscar nomination for best supporting actor.

The 1999 film, based on the Stephen King novel of the same name, starred Tom Hanks as a guard at a prison in the 1930s.

Duncan played John Coffey, a convicted murderer with a surprisingly gentle demeanour and extraordinary healing powers.

Duncan's performance impressed critics and moviegoers and he quickly became a favourite in Hollywood, appearing in several films a year.

He owed some of his good fortune to Bruce Willis, who recommended Duncan for The Green Mile after the two appeared together in Armageddon.

Duncan would work with Willis again in Breakfast of Champions, The Whole Nine Yards and Sin City.

He also appeared in the superhero film Daredevil and in comedies including Talladega Nights and School for Scoundrels.

His gravelly baritone alone was good enough for several animated movies, including Kung Fu Panda, Delgo and Brother Bear.

Born in Chicago in 1957, Duncan was raised by a single mother whose resistance to his playing football led to his deciding he wanted to become an actor.

But when his mother became ill, he dropped out of college and worked as a ditch digger and bouncer to support her.

By his mid-20s, he was working as a bodyguard for Will Smith, Jamie Foxx and other stars in Los Angeles.

He decided to quit that line of work – and pursue acting full-time – after the murder of rapper Notorious BIG, whom Duncan had been hired to protect before switching assignments.

Tom Hanks said: "I am terribly saddened at the loss of Big Mike. He was the treasure we all discovered on the set of The Green Mile. He was magic. He was a big love of a man and his passing leaves us stunned."

Source: guardian.co.uk