A monster crocodile has been pictured swallowing a four-foot bull shark whole on a riverbank in northern Australia.

Brutus, an 18ft crocodile believed to be more than 80 years old, has been a popular attraction with tourists visiting Adelaide River.

However, the 25 tourists on the river cruise got more than they bargained for when they spotted Brutus feasting on a shark.

Andrew Paice told Perthnow: "We'd fed Brutus on the bank earlier and were coming back past and we saw something in his mouth.

"The shark was still alive. Brutus took the shark back into the water and then started to shake it around a bit. He then went back into the mangroves like he was protecting his prey."

Brutus is easily identifiable by not only his huge size, but by his missing front leg – believed to have been lost in a shark attack many years ago.

Morgan Bowman, the operator of the cruise, said they occasionally see sharks in the river. "That's the first time I've ever seen one of our crocs catch a shark. It was amazing. It just shows for an old croc, Brutus is pretty quick," he said.

He added that passengers had reported seeing a four-foot shark in the river over recent days.

Brutus is well known among Adelaide residents. In 2011, he made headlines after bursting out of the water right beside a river cruise.

Lured by a dangling piece of kangaroo meat, the two-tonne monster jumped out of the water, giving onlookers quite a shock.

Speaking about Brutus' infamy, Bowman said: "We've got all these other crocs, nothing ever seems to happen to them. He's definitely got a bit of a reputation."