PERTH (Reuters) - A suspected great white shark has attacked a surfer off a Western Australian beach, biting off one of his legs.

Mr Ben Gerring, 29, a heavy machinery operator, was surfing at Falcon Bay Beach in Mandurah, south of Perth, on Tuesday when the shark attacked, media reported.

"A couple of the guys with longboards brought him in to the shore. So, it was obvious he wasn't in a good way and they were huddled around and in tears. It was really desperate scenes,"said Mr Nathan Hondros, a Mandurah Mail reporter who arrived on the scene shortly after the attack.

"He was unconscious. He'd lost his leg from above the knee so it was pretty horrific injuries. It was terrible to watch, there was a lot of distressed people on the beach. There were kids who were in the water surfing with him so it was a really, really difficult thing to watch."

The beach was closed and Mr Gerring, who is Australian, was taken to a hospital in Perth where he was in critical condition.

The Fisheries Department said a great white shark measuring at least 3m was likely to have been responsible given the injuries, the Nine Network reported.

Sharks attacked a record 98 people in 2015, researchers said in February.

The spike in attacks was attributed to rising human and shark populations.