An elderly man was attacked after being stopped while driving in Dianella on Tuesday afternoon.

The 74-year-old was travelling west along Yirrigan Drive about 2.45pm when a man crossed the street and stood in the middle of the road, forcing him to stop.

Police said the offender approached the blue coloured Saab before striking it with his hand and verbally threatening the driver.

“When the victim got out of his car to speak with the man, the man assaulted him, hitting him to the face several times,” a police spokeswoman said.

“The offender walked away and was last seen walking along Yirrgan Drive towards Farrier Road.

The victim was taken to St John of God Hospital to be treated for bruising to his jaw and face.

Police want to speak to a man they say is between 25 and 30 years of age, dark skinned and about 175cms tall with a medium build.

He had short black hair and facial stubble and was wearing a grey checked long-sleeve shirt, a white t-shirt and long pants.

Anyone with information should contact Crime Stoppers on 1800 333 000 or make a report online.