Two lions were killed after they severely mauled a man who stripped naked and entered their enclosure in an apparent suicide attempt, authorities said.

The man was taken to a hospital for treatment and was said to be in grave condition.

Director Alejandra Montalba of Santiago's Metropolitan Zoo said the venue was crowded with visitors when the incident happened on Saturday.

The 20-year-old man broke into the enclosure, removed his clothes and jumped into the middle, horrifying other visitors who witnessed the attack. Zookeepers killed the lions in order to save his life.

"The zoo has an established protocol, because people's lives are very important to us," said Montalba, adding that there were no fast-acting tranquilizers available to stop the lions from mauling the man.

She said she was deeply affected by the deaths of the two lions, a male and a female.

A zoo official was quoted by local media as saying, "These lions had been with us for more than 20 years."

Metropolitan Park director Mauricio Fabry said an apparent suicide note was found in the man's clothing. Witnesses reported that he also made religious proclamations.