A man riding an unregistered motorbike and carrying a stubby has crashed into a police car in Victoria, before trying to flee.

Police say the motorcycle struck the rear of the unmarked police car on Frankston-Flinders Road in Baxter at about 1.45am this morning.

"The rider, carrying a stubby, tried to flee the scene before he collapsed off the bike a short distance away," Victoria Police said.

The 45-year-old man was taken to hospital with minor injuries.

Police expect to interview him about riding an unregistered bike.