Motorbike rider found dead after 'hitting concrete barrier' on Monash freeway

Police are appealing for witnesses after a motorbike rider was found dead on the Monash Freeway in Melbourne's southeast last night.

A driver travelling outbound on the freeway near Malvern came across the rider lying on the road at about 9.20pm.

Police believe the rider hit a concrete dividing barrier on the highway, before being ejected from his bike more than 100 metres away.

"There must have been someone, at least one person who was also driving along at this time and must have witnessed what occurred," Detective Sergeant Mark Patrick from Victoria Police said.

The accident closed outbound lanes of the Monash Freeway between Toorak Road and the Winton Road overpass, as crash investigators examined the scene.

Police have urged anyone who witnessed the accident, or saw the rider before the crash to contact Crime Stoppers on 1800 333 000.