A man has died following a shark attack at Byron Bay on the New South Wales far north coast, paramedics say.

A NSW Ambulance spokeswoman said the man, aged 50, died on Clarkes Beach just after 11am.

Witnesses called triple-0 at 10.42am on Tuesday saying a man had been bitten by a shark at the southern end of the beach, off Lawson Street.

The NSW Ambulance spokeswoman said a doctor performed CPR on the man, who had a "very serious bite" on his leg, but he could not be saved.