A surfer has died after being attacked by a “very large” shark at Shelly Beach on the NSW north coast despite the brave attempts of his friends to save him.

Paramedics attempted to perform CPR on the 41-year old Japanese man at the popular tourist beach, near Ballina, around 9:45am (AEDT) today but he was pronounced dead at the scene.

He has been named as Tadashi Nakahara.

Mr Nakahara, who had been living in Ballina for around 12 months, suffered significant injuries to his legs in the attack and was helped to shore by four fellow surfers, two of whom were close friends.

Nakahara, centre, had been living in Australia for the past year. (9NEWS)

Police said the man died of blood loss and praised the efforts of the victim’s friends in their attempts to save their mate.

“We believe it was a very large shark,” Detective Inspector Cameron Lindsay said.

“Their actions were commendable.

“We have a situation where a significant amount of blood [was] in the water… they did their best.”

Pictured centre, Nakahara, 41, was a Japanese national. 9NEWS)

Police have closed beaches from South Ballina to Lennox Head for the next 24 hours and will work with shark experts before reopening.

Mr Lindsay said police were working with the Japanese consulate to inform Mr Nakahara's next of kin, who are believed to be in Japan.

Surfers who were in the water at the time reported seeing the shadow of the shark and estimated it to between 3.5m and 4m long.

Tadashi Nakahara, right, perished in the attack. (9NEWS)

NSW Life Saving Manager Andy Kent said surf life saving inflatable rescue boats, jet skis and the Ballina Jet Rescue Boat will remain on-scene to assist police in the search and to keep the public out of the water.

"This is obviously a very serious incident and we would ask that the public follow the directions of emergency service workers and lifeguards by remaining clear of the water," he said.

"Our thoughts go out to the man’s family and friends, who will dealing with this tragedy."

A 41-year-old Japanese man has died after being attacked by a shark near Shelly Beach, Ballina. (Supplied)

The attack is the second in the area in 24 hours.

Byron Bay surfer Jabez Reitman is recovering in hospital after a suspected shark attack 20km up the coast near Byron Bay yesterday.

The 35-year-old was sitting on his board about 60 metres off Seven Mile Beach early on Sunday morning when he was attacked from behind.

He didn't see what hit him and neither did a friend surfing with him, but he suffered a cut to his back and puncture wounds to his buttocks.

A friend drove the man to Byron Bay Hospital and he was later taken to Gold Coast Hospital where he is in a stable condition.