Australian police have found human remains while searching for a 12-year-old they believe was the victim of a crocodile attack.

The child was last seen on Tuesday, swimming with family near the remote Aboriginal town of Nganmarriyanga - about a 7-hour drive southwest of Darwin in the Northern Territory (NT).

“This is devastating news for the family, the community and everyone involved in the search,” said Senior Sgt Erica Gibson, adding that police would provide support to everyone impacted.

Earlier Sgt Gibson had told ABC News that a black crocodile had been seen in the immediate area.

As many as 40 members of the community helped police officers in their search for the child, which started shortly after the 12-year-old was reported missing. They scoured the area by foot, by boat and with the use of helicopters, covering challenging terrain with thick vegetation and a narrow, winding waterway.

No details were given on whether the crocodile suspected to have attacked the child had been found.

Earlier on Wednesday NT Police Minister Brent Potter said wildlife officers had been authorised to "remove" the crocodile from the area once it was located and reiterated the government's safety message.

"We live in a place where crocodiles occupy our water places... it's just a reminder to stay out of the water as best we can."

Found all around the northern edges of Australia - from Broome in Western Australia to Gladstone in Queensland - saltwater crocodiles were hunted to near extinction but numbers have bounced back since the practice was banned in the 1970s.

The NT is now home to an estimated 100,000 saltwater crocodiles, more than anywhere else in the world. Attacks though are uncommon.

There have been at least two other crocodile attacks in the NT in the past year - a nine-year-old boy who was injured in January while swimming in Kakadu National Park, and a farmer who escaped a beast's jaws by biting it back in October - but there has not been a fatal attack there since 2018.

Queensland, however, has had a series of deadly attacks in recent years, including a 16-year-old boy who was killed in the Torres Strait in April.