The former US bus driver jailed for life for kidnapping and raping three young women he held as sex slaves for a decade was found hanged in his cell late Tuesday, authorities said.

The death of Ariel Castro brought an abrupt and dramatic ending to a sordid case that shocked America and the world with its revelations of systematic sexual depravity and brutality.

Castro was found hanged in his cell, the Ohio Department of Corrections said in a statement carried widely by US news outlets.

The circumstances of his hanging were not immediately clear. He had been in solitary confinement.

Officials tried in vain to resuscitate the 53-year-old, according to the statement.

"He was housed in protective custody which means he was in a cell by himself and rounds are required every 30 minutes at staggered intervals. Upon finding inmate Castro, prison medical staff began performing life-saving measures," the statement said.

Castro was pronounced dead at 10:52 pm.

"A thorough review of this incident is underway," the statement by corrections department spokeswoman JoEllen Smith said in the statement.

Blogs posted in the main Cleveland newspaper, The Plain dealer, were merciless.

"Adios diablo, may you burn for 1,000 years, just like you were sentenced," one said, alluding to his jail term of life plus 1,000 years.

"Why no picture of him hanging? Now THAT would be justice," asked another.

Smith and other corrections department officials were not immediately reachable for comment.

Castro's crimes -- keeping the three young women in what came to be known as a house of horrors and raping and otherwise brutalizing them for around a decade -- disgusted the country and led to an outpouring of national pity for the three victims. They were abducted separately between 2002 and 2004.

Their names are Amanda Berry, now 27; Gina DeJesus, 23; and Michelle Knight, 32.

They ranged in age from 14 to 20 when Castro took them off the street in a working class neighborhood of Cleveland, under the pretext he was offering them a ride in his car.

They escaped on May 6 when Berry managed to break open part of the front door and call out to a neighbor for help. Her frantic telephone call later to emergency rescue services was played and replayed over the media in the days after the three women escaped.

At the trial, as Castro -- a pudgy, balding man in wire rim glasses -- sat in a bright orange prison jumpsuit, it emerged that they were brutalized, sometimes chained up and kept in abysmal conditions.

Berry had a daughter fathered by Castro.

The white delapidated house where they were tormented was demolished a few days after Castro was sentenced.

At his sentencing hearing August 1, Castro had insisted he was not evil but rather addicted to sex.

"I'm not a monster. I'm sick," he pleaded.

Despite having pleaded guilty to 977 charges related to his victims' brutal decade-long ordeal, including many rapes and the murder of a foetus through beating its mother, Castro said he was not a violent man.

He pleaded guilty after prosecutors agreed not to seek the death penalty.

Castro said he had himself been sexually abused as a child and had grown up obsessed with sex, addicted to pornography and a compulsive masturbator.

He said he had not plotted the three kidnaps, but had acted on impulse.

"I am not a monster. I am a normal person. I am just sick. I have an addiction just like an alcoholic has an addiction," he said.

On that same day, The Plane Dealer ran a cartoon mocking Castro's attempt at defense and alluding to the fact that he played bass in a salsa band. The drawing shows him standing in front of the judge's stand and holding the instrument.

"For my swan song I will be performing The Rolling Stones' 'Sympathy for the Devil,'" the Castro figure says in the vignette.

Michael Russo, the judge who sentenced Castro that day, described his crimes as unspeakable.

"Sir, there is no place in this city, there is no place in this country and indeed there is no place in this world for those who enslave others, those who sexually assault others and those who brutalize others," Russo said.

A tearful Michelle Knight, who was kidnapped at the age of 20, said in emotional testimony before the court that death would have been "so much easier" for her tormenter.

"I spent 11 years in hell, and now your hell is just beginning," Knight told Castro.