The remains of an Australian man who went missing on a fishing trip in crocodile-infested waters have been found inside two of the reptiles, police said Wednesday.

The 65-year-old victim, named in Australian media as Kevin Darmody, had gone fishing on Saturday in far north Queensland as part of a group, who shooed away a crocodile so they could start fishing, police said.

People fishing with the pub manager heard him "yell, scream very loudly, followed by a large splashing of water", said Cairns police inspector Mark Henderson.

Rangers later used rifles to shoot and kill two crocodiles - one measuring about 4.2 metres and the other 2.8 metres - found upstream from where the group was fishing within Lakefield National Park.

Examinations found human remains in both of the predators, police said.

Henderson described it as a "tragic, tragic ending".

The man was "a very nice fellow" from the rural north Queensland town of Laura, which has a population of about 130 people, Henderson said.

Queensland state wildlife official Michael Joyce urged people to be wary.

"This is croc country. If you are in water and especially if you are in Lakefield, which is declared specifically for crocodile conservation, you should expect crocodiles in that water."