Police are investigating a collision between a truck and cyclist at Mornington this morning.

It is believed a concrete truck was travelling north-west on Beleura Hill Road when it collided with a cyclist travelling in the opposite direction around 6.45am.

The cyclist, a 34-year-old Mt Eliza man, was hit by the truck and knocked from his bike.

He has been airlifted to The Alfred hospital suffering life threatening injuries.

The 57-year-old male truck driver, from Woodleigh Vale, is currently assisting investigators with their enquiries.

Beleura Hill Road is currently blocked between Barkly Street and Shandon Street while police investigate.

Investigators urge anyone who may have witnessed the incident to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au