A teenage boy has serious injuries after being bitten by a shark at a beach on the NSW North Coast.

Emergency services were called to Cabarita Beach, between Tweed Heads and Byron Bay, at 3.50pm on Sunday after the attack.

The teen suffered injuries to his right upper arm, wrist and right leg.

He was airlifted to to Gold Coast University Hospital by the Westpac Rescue Helicopter in a serious but stable condition.

Surfers and an off-duty paramedic from just over the border in Queensland were on the beach at the time and rushed to his aid, applying a tourniquet to stem the bleeding.

A second chopper went looking for the shark.

Cabarita Beach will be closed for 24 hours.