The man was surfing at Main Beach about 6.20am on Friday.

Around 6am, the 52-year-old man spotted what he believed to be a shark and shouted out to the other surfer to get out of the water.

As he paddled towards shore, the 52-year-old was attacked by the shark which bit his left leg.

The impact knocked the man off his board and in an attempt to scare the shark away, the man punched it. During the struggle, the shark also bit his left arm.

The man eventually made it to shore where a passer-by applied a tourniquet to his leg.

Two paramedics worked to stabilise the patient while a police officer began the drive to Lismore Hospital.

A short time later, a NSW Ambulance vehicle with a doctor and paramedic on board met the ambulance. The doctor and two paramedics worked on the patient while the third paramedic drove them to Lismore Hospital.

The police officer drove the empty vehicle the doctor had arrived in back to its base in Lismore.

The 52-year-old man is now at Lismore Hospital undergoing treatment.

Main Beach and two other local beaches – Shark Bay and Chinamans Beach – have all been closed until 6.30am Saturday. The situation will be re-assessed on Saturday morning.

There have been several sightings of sharks up to five metres long in the beaches around Evans Head and Ballina in recent days.

Bart Easdown from the Evans Head Riverfront Kiosk said locals had been sharing information in a Facebook group.

"There's been a lot of sightings including a couple of four-metre and five-metre ones up the coast," he said. "And someone spotted a small one around Evans Head."

A four-metre shark was spotted at Boulder Beach and Shelley Beach on Thursday.

Beaches around nearby Ballina were closed on Sunday after a 3½ metre long shark was spotted off the coast. 

The shark was seen in the same area in which body boarder Matt Lee was mauled by a similar-sized great white shark three weeks ago.

In February, 41-year-old Japanese surfer Tadashi Nakahara died after being bitten by a shark at Shelley Beach near Ballina.