Fisherman taken by croc in NT

A 57-year-old fisherman is believed to have been attacked and killed by a crocodile in front of his wife while they were fishing in the Northern Territory.

The man entered the water to unsnag his fishing line on the Adelaide River and appears to have been taken by a crocodile, Northern Territory Police Duty Superintendent Jo Foley said.

"The initial information is that she (the man's wife) did not see him taken but (heard) a scream and then turned around and saw a (crocodile) tail splashing in the water," Supt Foley said.

"She is absolutely distraught and we're holding really grave concerns for his welfare."

The couple were fishing near the Adelaide River bridge on the Arnhem Highway.

The Adelaide River is known for its crocodile population and attracts tourists who cruise its waters to see the reptiles.

Supt Foley said the man's wife raised the alarm after the attack around 5.30pm.

A police search involving two boats was being carried out on Monday night and would continue into the morning, she said.