A 16-year-old girl was killed Saturday after being mauled by a shark as she swam in a river in Western Australia, officials said.

The girl was critically injured when an unknown species of shark bit her in the Swan River in the Perth suburb of Fremantle, a state government statement said.

She was pulled from the water but pronounced dead at the scene after efforts to revive her failed, said Paul Robinson, police acting inspector for the Fremantle district.

"It's very early on, what we're being advised is that she was with friends on the river," he told a news conference.

"They were on jet skis. Possible a pod of dolphins were being seen nearby and the young female jumped in to swim nearby the dolphins."

Describing it as a "very, very traumatic incident," Robinson said the family of the girl, who was from Perth, were "absolutely devastated by the news".

Fisheries experts had advised that it was unusual for sharks to be found in that part of the river, he said.