A knife-wielding home invader who punched a woman in the face has been hit by one or more vehicles on a highway after fleeing the scene, police say.

The man allegedly smashed a window as he entered a home in the eastern Perth suburb of Westminster armed with a knife just after 7:00am today.

The occupant, who heard the sound of glass breaking, confronted him and he punched her in the face before escaping.

The woman received a minor injury from the punch.

Police believe the man was then struck by one or more vehicles after he ran into traffic on Reid Highway.

He was seriously injured and taken to Royal Perth Hospital.

Part of the highway was closed for some time earlier today.