A man was left fighting for his life following a shark attack on the New South Wales mid north coast.

The 32-year-old was body-boarding at Ballina with friends when he was bitten this morning.

He is suffering significant injuries to his lower legs and has been flown to Gold Coast hospital in a critical condition.

Liam Howlett from Surf Life Saving Australia said that at this stage it too early to say what type of shark was involved in the attack.

"The Department of Primary Industries will be investigating what the species of shark is and at this stage it is unclear the species of shark involved in the attack. Obviously an investigation will be done in due course."

Ballina Mayor, David Wright, said a large shark was seen in the area afterwards and they think it was a great white.

A surfing competition is due to start in Ballina tomorrow, but all beaches in the area have been closed for at least 24 hours.