A group of Australian teenagers have been hailed as heroes after diving into the ocean to save a friend who fell victim to a brutal shark attack.

On Saturday, the 14-year-old had been fishing on Australia's Torres Strait Islands before deciding to take a dip at around 6.23pm.

But shortly after entering the water, he was suddenly bitten on the torso by an unseen shark.

After seeing the commotion, witnesses who are believed to be friends of the teenager selflessly plunged into the dangerous water to drag the him on to the beach.

The 14-year-old victim had been fishing on Australia's Torres Strait Islands before deciding to take a dip

The victim was quickly rushed to Thursday Island Hospital after suffering “significant abdominal injuries”, according to Queensland Police.

The 14-year-old is also believed to have lost a large amount of blood and has suffered life-threatening injuries to his internal organs.

He was later flown to Townsville University Hospital on the mainland, where he remains in critical condition.

Local authorities from the Torres Strait Islands have praised the teenagers who likely saved the victim's life after bringing him to shore.

Shortly after entering the water, he was suddenly bitten on the torso by an unseen shark (file photo)

Torres Shire Council wrote on social media that the group "acted with incredible bravery and quick thinking to help him back to safety".

Mayor Elsie Seriat said the 2,800-strong community on the small island "feels this deeply".

She said: “This incident is very unfortunate, and our hopes and prayers go out to the boy and his family at this difficult time.

"Public safety is of paramount importance... We strongly encourage everyone to be mindful and aware of the dangers in our surrounding waters and to always use good judgment.

“We know many people are thinking of the young boy, his friends, and their families. Please continue to keep them in your hearts and prayers.

“We want to express our heartfelt thanks to the boys who helped their friend, and to the QAS, QPS, Queensland Health, and RFDS teams for their swift and compassionate response.”

Ms Seriat said the local authority will try to make improvements to signage and education of water safety in the wake of the attack.

Queensland Premier David Crisafulli told ABC that he is thinking of the boy and the Torres Strait Islands community at this time.

Queensland Premier David Crisafulli said he was thinking of the boy and the Torres Strait Islands community

Mr Crisafulli said: "It's obviously very traumatic for the individual, for the family, for the first responders, for those in the Townsville hospital who are administering treatment.

"I just hope everything is okay."

The species of shark that mauled the 14-year-old boy is still yet to be determined.

Australia records roughly 20 shark attacks every year, with bull sharks, great white sharks and tiger sharks being the most common perpetrators.

Since 1911, there have been 66 recorded shark bites in the Torres Strait Islands.