Police and emergency services crews are searching waters off a remote South Australian beach after what is believed to be a fatal shark attack.

SA Police said a 55-year-old man was surfing near Granites Beach, south of Streaky Bay on the Eyre Peninsula, about 10.20am on Tuesday when witnesses reported seeing a shark attack him.

Initial reports were of a serious attack, but police confirmed later on Tuesday the man was believed to be dead.

“Eyre and Western Police immediately responded and initiated a search with the assistance of Police Water Operations, PolAir, State Emergency Service and local volunteers,” they said.

“The man’s body is yet to be found and the search will continue through to day’s end.”

Streaky Bay is about 300 kilometres north-west of Port Lincoln, and more than 700 kilometres from Adelaide.

Tuesday’s incident follows another fatal shark attack at Elliston, also on the Eyre Peninsula, in May. Local school teacher, Simon Baccanello, 46, is believed to have been mauled to death while surfing 30-50 metres from shore.

It is also less than four weeks since 64-year-old Pamela Cook suffered serious leg injuries when she was bitten by a shark at Beachport on the state’s south-east coast.

– with AAP