<p>Sydney: A shark killed a diver off the coast of Western Australia on Saturday, police said, the country's fourth fatal shark attack this year.</p> <p>The man in his thirties was attacked by a 4.5-metre (15-foot) shark off Michaelmas Island, southeast of Perth, ambulance services and the Western Australian government said.</p> <p>The attack was reported around 11:25 am (0325 GMT), they added.</p> <p>Police said the man was spearfishing when he was attacked by the deadly fish and was taken back to shore where paramedics attempted to treat him.</p> <p>"Sadly, he was unable to be revived," they said.</p> <p>The state's Department of Primary Industries and Regional Development urged people to take "additional caution" in the area and to stay abreast of shark sightings in the area.</p> <p>The attack comes just two weeks after a man was killed by a shark in northern Queensland state.</p> <p>And the killing is the second this year in Western Australia -- last month a man died after being attacked by a great white off Rottnest Island near the city of Perth.</p> <p>Australian scientists believe increasingly crowded waters and rising ocean temperatures are shifting sharks' migratory patterns, which may be contributing to a rise in attacks.</p> <p> </p>