A cassowary has killed its owner in the US state of Florida by attacking him after he fell over.

The Alachua County Fire Rescue Department told the Gainesville Sun that a cassowary killed the man on Friday on his property, likely using its long claws.

The victim's name was not released.

Alachua County Fire Rescue Deputy Chief Jeff Taylor said the man was taken to hospital about 10am Friday but died there.

"It looks like it was accidental. My understanding is that the gentleman was in the vicinity of the bird and at some point fell. When he fell, he was attacked,” Taylor told the Gainesville Sun.

A Florida Fish and Wildlife Conservation Commission spokeswoman said they had been told the man was breeding the birds.

The commission lists cassowaries as being dangerous to people and says "substantial experience and specific cage requirements must be met”.

Meanwhile the man's long-term partner told the Florida paper he had died "doing what he loved”.

Cassowaries are large, flightless birds native to Australia and New Guinea similar to emus that stand up to 1.8 metres tall and weigh up to 60 kilograms.

The San Diego Zoo's website calls them the world's most dangerous bird with a 10 centimetre, dagger-like claw on each foot that can cut open people or predators.

They have black body feathers and bright blue heads and necks.

They are not raised for food, but are sought after by collectors and it is estimated there are fewer than 1000 in the wild..