A boy and his father have spent the night in hospital after a dog attacked them at their Como home yesterday afternoon.

Larissa Miller says her nine-year-old stepson Jai Cooper was riding his scooter in their driveway on Wooltana Street when a Staffordshire Bull Terrier cross latched onto his arm.

When his father tried to remove the dog, it started attacking him.

Jai was taken to Princess Margaret Hospital for treatment and his father was taken to Royal Perth Hospital with serious injuries.

Ms Miller says her partner has been in surgery for 11 hours.

"Because he tried to rip it off, it's actually ripped his thumb off, and he was on the ground and it was just attacking him everywhere," she said.

"He's a qualified chef; a boxer - he needs his hands.

"This dog, you could see wasn't going to stop.

"He had a big chunk taken out of his side, he's been in surgery 11 hours."

Ms Miller says the dog, which belongs to a neighbour, jumped over its fence and came into their yard.

She has called for the dog to be destroyed.

The City of South Perth says rangers have seized the dog and are working with police to investigate the incident.