An unidentified family member earlier told TMZ - the first outlet to report that Jackson had suffered a cardiac arrest - that the star was in "really bad shape."

Michael's father Joe Jackson told E! Online he was aware of the emergency but did not know further details.

"I am in Las Vegas, but yes, people in Los Angeles called me and are with Michael and tell me he was taken to the hospital,'' he said.

"I am not sure what's wrong. I am waiting to hear back from them.''

The LA Times said paramedics were called to a Bel Air home off Sunset Boulevard that Jackson had been renting for $100,000 a month.

The reports came as Jackson prepared to make a keenly anticipated concert comeback - billed as "the final curtain" - in London, his first series of shows in more than a decade and the first since his 2005 acquittal on child molestation charges.

However those concerts had been thrown into doubt after Jackson pushed back the opening dates last month.

Organisers of the concerts at the time stressed the delay was not linked to Jackson's health.

While Jackson reigned as the King of Pop in the 1980s, his once-stellar career had been overshadowed by his his startling physical transformation and multiple allegations of child abuse.

Jackson lived as a virtual recluse following his 2005 acquittal on charges including child molestation and plotting to kidnap his young accuser.

Jackson is still worshipped by fans for revolutionising music, dance and music videos at the peak of his success.