Sickening audio has now surfaced of Joran van der Sloot confessing on tape to murdering Natalee Holloway … bashing her head with a cinder block on the beach.

The chilling confession, released by the court, includes Joran describing his night with the 18-year-old Alabama native on a beach in Aruba back in 2005. Joran says in his confession they started kissing, but she denied his sexual advances and kneed him in the groin, which set him off.

He says he kicked her in the face, then grabbed a nearby cinder block and “completely” smashed her head in. Joran disturbingly says it was dark, but he could see her face had collapsed in as a result of the cinder block.

Joran claims he was scared and didn’t know what to do after the attack … which is when he says he put her body into the ocean.

Remember, Joran entered a guilty plea in Alabama on Wednesday to charges of wire fraud and extortion after telling Natalee’s family he’d give details about her death in exchange for money.