A shark mauled a boy swimming in Sydney Harbor on Sunday, leaving him in critical condition with serious leg injuries, authorities said.
The predator bit the boy, believed to be about 13 years old, during the late afternoon off Shark Beach, New South Wales state police said.
"The injuries are consistent with what is believed to have been a large shark," police said in a statement.
Officers pulled the boy from the water off the harbor beach within minutes of being alerted to the incident, police said.
They gave the boy first aid for "serious" leg injuries while he was aboard a police boat, applying two medical tourniquets.
Paramedics transported him to Sydney Children's Hospital, where he was said to be in critical condition.
"Swimmers are advised to avoid entering nearby waters at this time," police said.
Shark Beach, in Sydney's eastern suburb of Vaucluse, was closed and police evacuated nearby beaches in the harbor, the state government said.
Wildlife experts were working to identify the shark species involved, it said in a statement.
"This is a tragic shark attack on a young boy having a swim on a Sunday afternoon near a harbor beach in Sydney's east," New South Wales Agriculture Minister Tara Moriarty said.
"Our thoughts are with the young boy and his family. I understand there were also other young people with him at the time of the attack, our thoughts are also with them."
There have been more than 1,280 shark incidents around Australia since 1791, of which more than 250 resulted in death, according to a database of the predators' encounters with humans.
Increasingly crowded waters and rising ocean temperatures that appear to be swaying sharks' migratory patterns may be contributing to a rise in attacks despite overfishing depleting some species, scientists say.
A great white shark mauled surfer Mercury Psillakis to death at a popular northern Sydney ocean beach in September.
Two months later, a bull shark killed a woman swimming off a remote beach north of Sydney.
