Police on Monday recovered the body of a man taken by a large crocodile in northern Australia with rangers confident they have killed the animal responsible.

Sean Cole, 26, was snatched on Saturday in front of at least 15 traumatised onlookers as he swam with a friend across a muddy river that has one of the highest densities of saltwater crocodiles in the world.

Northern Territory police senior constable Wade Rodgers said his body was found early Monday in the area where he was last seen.

"Our thoughts are with the family during this very difficult time," he said.

Witnesses had recounted seeing the animal, believed to be nearly five metres (16 feet) long, swimming upriver with his body in its jaws.

Cole had been celebrating a friend's 30th birthday on Saturday at the Mary River Wilderness Retreat, about 110 kilometres (70 miles) from the city of Darwin, when he decided to plunge into the water. His friend survived.

The Northern Territory News said a survey three weeks ago recorded four crocodiles over four metres in the area and 10 to 12 measuring more than three metres.

Parks and Wildlife Ranger Tom Nichols said four crocs had been shot, including the one believed to be responsible for the attack.

"Any animals that were in that range which we believed to be a possible target in the area where the accident took place, we usually take them out for simple reasons," he told ABC radio.

"We do autopsies on those and it's also closure for the families if there's anything there."

Saltwater crocodiles, which can grow up to seven metres long and weigh more than a tonne, are a common feature of Australia's tropical north.

They have been protected since the 1970s and their numbers have increased steadily since, along with the number of human encounters.

In December, a nine-year-old boy was taken by a four-metre crocodile while swimming in the Northern Territory, one month after a seven-year-old girl went missing while swimming, also in the north.

Source: AFP