A cyclist may have swerved to avoid a car door when he was fatally struck by a truck in Dunedin this morning, police say.

The male cyclist was killed about 10am and police were still working on identifying him.

He was struck by a truck and trailer unit while travelling north on Cumberland Street, State Highway One, senior sergeant Kelvin Lloyd said.

It was understood he may have come in contact with the truck after swerving to avoid a car door, Lloyd said.

"There's a suggestion that may have been an issue but it's just one of the things we're looking at."

Police were speaking to the driver of the truck and the driver of a vehicle which was parked when the incident took place, Lloyd said.

Serious crash investigators and other police staff were at the scene.

Dunedin police were keen to hear from anyone who may have witnessed the incident.

Anyone with information was urged to contact Dunedin police on 03-471 4800 or provide information anonymously via Crimestoppers on 0800 555 111.

Detours were in place around Cumberland St and were likely to remain in place over the next couple of hours. 

- © Fairfax NZ News