A man who was attacked by a crocodile while swimming in a popular lake in WA’s north has been transferred to Royal Perth Hospital for treatment.

The 67-year-old was swimming near a houseboat on Lake Argyle when he was bitten by a suspected freshwater crocodile in the Hicks Passage area.

Three people who tried to help the man were also bitten.

The man was taken to Kununurra Hospital under lights and sirens before being transferred to Royal Perth Hospital on Sunday.

He remains in a stable condition while undergoing treatment for multiple injuries.

The others involved were treated at the scene.

The Department of Biodiversity, Conservation and Attractions are continuing to monitor the situation and will conduct patrols in the area early next week.

“Anyone who encounters a freshwater crocodile that is interacting with people swimming, fishing, camping or boating is encouraged to report it to their local Parks and Wildlife Service office, along with a photo of the crocodile and GPS location if safe to do so,” a DBCA spokesperson said.

“Lake Argyle is home to a large population of freshwater crocodiles which, while not usually considered dangerous animals, have the potential to inflict serious injuries.”

The spokesperson said Lake Argyle is not managed by DBCA but department staff may remove a freshwater crocodile from the area if it is identified as actively presenting a threat to humans.

Freshwater crocodiles are known for being less aggressive towards people making an attack like this very rare.

Despite the scare, the annual Lake Argyle Swim open went ahead on Saturday.

Four hundred swimmers hit the water taking on a modified course.