A man who entered the lions' enclosures in a Kiev Zoo shouting and questioning the existence of God was mauled to death by a lioness.

"The man shouted 'God will save me, if he exists', lowered himself by a rope into the enclosure, took his shoes off and went up to the lions," the official said.

"A lioness went straight for him, knocked him down and severed his carotid artery," he added.

The incident happened Sunday when the zoo was packed with visitors.

The Zoo keeps the lions and tigers in an "animal island" protected by thick concrete blocks.