Traffic diversions are in place following a collision between a truck and motorised bicycle on the Henty Highway near Portland. 

Police said the truck was travelling north on the Henty Highway when it collided with the bicycle about 5.30pm.

The cyclist, an 18-year-old Portland man, died at the scene.

The truck driver, also a Portland man, stopped at the scene and is assisting police with their inquiries.

No one else was injured during the incident.

Portland police Sergeant Sean Elliot a section of the road was currently closed and people should take alternative routes. 

"The Highway Patrol unit and a senior sergeant are out on the scene with CFA, SES and VicRoads," he said. 

Investigations are ongoing. Anyone with information should contact Portland Police or Crime Stoppers on 1800 333 000.

Earlier, 6pm: 

A male cyclist has been killed in a collision involving a truck at Portland.

Police sources said the accident happened soon after 5.30pm.

The accident is listed on the emergencyvic website as being on the Henty Highway, just south of Bridgewater Road, at the intersection with Wyatt Street.

Further details to come.

It's the third cyclist to die on south-west roads since December last year.

Allansford teenager Sam Chilton, 16, died in an accident involving a truck, on his way to cricket training, nine days ago.

His funeral was held on Friday.

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