SYDNEY, April 26 -- Great white sharks and bull sharks feeding on a washed-up whale carcass have forced the closure of a string of beaches south of Sydney, Australian wildlife and surf rescue authorities said Sunday.

The eight-metre (26-foot), 25-tonne sperm whale carcass was reportedly spotted on Saturday lying on wave-swept rocks at Era beach in the coastal Royal National Park, leading to immediate beach closures.

"There's some great white sharks and there's also some bull sharks being sighted there," said Brendon Neilly, area manager for the New South Wales National Parks and Wildlife Service.

"While they can be fairly dramatic and confronting events for people, they are eminently natural events, and so the whale carcass is being mo...