Melbourne Cup-winning trainer Danny O'Brien has expressed his heartbreak after the death of one of his track riders in an accident near Geelong in Victoria.

The registered stablehand was killed after a car struck a horse he was riding on Thirteenth Beach Road at Connewarre on Monday morning.

The man, aged in his 30s, died at the scene while the driver of the car and the horse were reported to have minor injuries.

O'Brien issued a statement on Monday afternoon.

"It's with a heavy heart and tremendous grief that we confirm an incident that claimed the life of one our staff this morning," he said.

"Our thoughts, prayers and support are with the family of our friend and colleague and all our team. We are completely heartbroken.

"We have had some tough days in this industry, but they are nothing compared to the heartbreak and sadness of today.

"We ask that the privacy of our staff to be respected as they come to terms with today's tragedy.

"It appears that the horse in question of the incident has only minor injuries, however our vet will continue monitoring its progress. Our owners of this horse have been notified."

Racing Victoria and its Stableline counselling program are assisting O'Brien and his staff across his stables at Barwon Heads and Flemington.

"RV extends its sincere condolences to the family and friends of the track rider, some of whom are yet to be notified," RV said in a statement.

O'Brien has a 160-acre private training complex at Thirteenth Beach as well as stables at Flemington and has credited the beach surrounds with helping Vow And Declare to his success in last year's Melbourne Cup.

Victoria Police and WorkSafe are investigating the circumstances of the incident.