A surfer has died after he was bitten by a shark on the NSW North Coast on Sunday morning.

NSW Police said emergency services were called to Shelley Beach, at Emerald Beach, north of Coffs Harbour on Sunday morning just before 11am.

Police said the man had critical injuries to his right arm and back.

Bystanders tried to deliver CPR and paramedics took over but the man died at the scene.

NSW Ambulance Inspector Chris Wilson said it was a "devastating" incident for everyone on the beach at the time.

"A number of local surfers and bystanders came to the aid of this man, they were incredibly brave in a very challenging situation," Mr Wilson said.

"The patient suffered a critical injury to his arm, but despite the best efforts of bystanders, paramedics and other emergency services, the patient couldn't be revived."

A report will be prepared for the coroner.