Cyclists entering Melbourne's CBD will face fines of hundreds of dollars if they disobey the road rules under a police crackdown beginning today.

Police will patrol major routes into the city at peak times following a recent jump in bicycle crashes that have left some cyclists with serious injuries.

Senior Sergeant Dale Huntington said four cyclists had died on Victorian roads this year, and in recent months several cyclists had been injured after riding into car doors on St Kilda Road.

Bike-related laws to be enforced include failing to wear a helmet (a $146 fine), not having lights ($146), failing to obey a traffic light ($292) and riding in a tram safety zone ($292).

“We have seen a number of incidents recently, particularly in the St Kilda Road area, where cyclists have collided with opening car doors," Senior Sergeant Huntington said.