PERTH, Australia - A shark killed an American out diving off a popular Australian tourist island on Saturday, in the third fatal shark attack off the country's west coast in two months, police said.

The man, a US national, was killed while diving alone off Rottnest Island, a popular getaway in the Indian Ocean about 20 km (12 miles) west of the Western Australia state capital, Perth. ?

A police spokesman told Reuters the body surfaced with "obviously traumatic fatal injuries".

Witnesses said the shark was a three-metre white pointer, the spokesman said. The victim, thought to have been 32 years old, has not been named.

Sharks are common in the waters around Australia. Attacks on humans are normally rare, but fatal attacks periodically occur.