The family of a 12 year old boy who was savagely attacked by a shark in Sydney Harbour on Sunday have shared a heartbreaking update on his condition following the terrifying incident.

The youngster, identified in the Australian media as Nico Antic, was enjoying a day at the beach with friends at Shark Beach in Sydney Harbour.

The group were leaping off rocks at the end of the beach when he was attacked by what is believed to be a bull shark, The Mirror reports.

This shark attack was the first in a series of four other maulings that have occurred in the days since Nico was hospitalised. Emergency services arrived at the scene within minutes on Sunday and have since commended Nico's friends for their courage, as they entered the water to rescue him.

Nico was swiftly taken to Sydney Children's Hospital in a critical condition.

Both of his legs were severely damaged in the attack, with medical professionals working tirelessly to save the boy, who underwent emergency surgery on Sunday night. His family have now revealed Nico's bleak prognosis, informing the Daily Mail that he has been in a coma since the devastating attack.

His sister, Sophie, expressed her family's sorrow, telling the Daily Mail that Nico is "still asleep, but will not be able to make it because his brain is completely unresponsive". Sophie added: "He is a sporty kid and never fails to put a smile on people's faces. He is loved by many friends and family."

The heartbreaking news comes just a day after family friend Victor Piñeiro launched a GoFundMe campaign to aid the Antic family. He shared a similarly distressing update on Tuesday about Nico's condition, alongside the fundraiser to support his family during this unimaginably difficult period.

"Despite all efforts, this heartbreaking event has led to the worst possible outcome," he penned. "We are raising funds to help the Antic family cover upcoming expenses and related arrangements during this incredibly difficult time."

Approximately 1,700 people have contributed to the family so far, and as of 2.30pm local time, they had amassed just over AUD$122,000 (£61,000).

Nico was the first casualty in a series of shark attacks across the Australian state of New South Wales in the subsequent days. Swimming areas on NSW's northern beaches were shut down yesterday for both surfers and swimmers for 48 hours following a 39 year old man becoming the fourth individual attacked since Sunday.

On Monday, a 27 year old man sustained critical injuries after being bitten at North Steyne Beach in Manly, on Sydney's northern beaches. NSW Police report that the man has suffered "life-changing injuries" from the attack and remains in a critical condition post-surgery.

In another incident on Monday, another surfer narrowly escaped unscathed after a shark bit a chunk out of his surfboard at Dee Why Beach on NSW's northern beaches.

Shark experts have warned that the current conditions in New South Wales - warm ocean temperatures and murky water due to recent storms - are creating an ideal environment for bull sharks.

Steve Pearce, the chief executive of Surf Life Saving NSW, told ABC, Australia's national broadcaster: "Anytime after a big weather event there's always going to be a lot of run-off and out flow of creeks into the ocean and river mouths.

"We really strongly advocate that nobody swim or surf near river mouths because it's obviously an area where sharks congregate. If it's dirty water I'd think twice about going in there."

Pearce further cautioned: "We have such poor water quality that's conducive to bull shark activity ... [so] just go to a local pool, because at this stage, we're advising that the beaches are unsafe."

Donations can be made to the Antic family via their GoFundMe campaign here.