A seven-year-old boy broke into a zoo in central Australia and fed several live animals to a crocodile while bashing others to death with a rock.

The boy killed 13 animals worth around A$7,000 (£3,070), including a turtle, bearded dragons and thorny devil lizards after scaling a security fence at the Alice Springs Reptile Centre in the Northern Territory on Wednesday, said the zoo's director, Rex Neindorf.

In 30 minutes he used a rock to kill three lizards, including the zoo's beloved 20-year-old goanna, which he fed to a 3.3m (11ft) saltwater crocodile named Terry that weighs 200kg (440lb).

The boy was caught on security camera as he threw live animals to Terry over the two fences surrounding the crocodile's enclosure.

At one point he climbed over the outer fence to get closer to the crocodile. Neindorf said the boy's face looked blank in the footage. "It was like he was playing a game."

The animals were not rare but some would be difficult to replace, said Neindorf. "We're horrified that anyone can do this, and saddened by the age of the child."

Alice Springs police said they had identified the local boy but could not press charges because of his age. Children under 10 are not criminally liable in the Northern Territory.

"By all accounts he's quite a nasty seven-year-old," said Neindorf, who plans to sue the boy's parents. "If we can't put the blame on to the child, then someone has to accept the responsibility."

The zoo's security system, which relies on sensors, probably did not detect the boy because of his size, Neindorf said