Oscar-winning soul legend Isaac Hayes has died aged 65.

A family member reportedly found Hayes, who once described himself as a "health fanatic", unresponsive near a running treadmill.

He was pronounced dead at Baptist East Hospital in Memphis, Tennessee, but the cause of death was not immediately known.

Hayes' theme song from the film Shaft became a worldwide hit in 1971.

He won an Academy Award for Theme From Shaft and was nominated for another one for the score. The song and score also won him two Grammys.

He had already made his mark as a songwriter, penning the classics Hold On, I'm Coming and Soul Man for Sam and Dave along with David Porter for legendary soul label Stax in the early '60s.

His 1969 album "Hot Buttered Soul" made Hayes a star, with his shaven head, gold chains and sunglasses giving him a compelling visual image.

In 1997 he became the voice of Chef, the school cook and devoted ladies man on the animated TV show South Park - but he left the show because he disagreed with its attacks on Scientology.

Hayes was elected to the Rock and Roll Hall of Fame in 2002.

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