A motorbike rider has died and another has been left fighting for life following a collision between two bikes and two cars on a Melbourne freeway.

The vehicles crashed on the Western Fwy in Grangefields, near Melton, about 11.20pm on Saturday.

One of the riders, who is yet-to-be-formally identified, died at the scene.

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The other motorbike rider was taken to hospital with life-threatening-injuries.

The drivers of the vehicles were not injured and stopped at the scene.

“Police are working to establish the circumstances surrounding the collision,” Victoria Police said.

Anyone who witnessed the incident, has dashcam footage or any other information is urged to contact Crime Stoppers.