A Melbourne driver who went to assist people involved in a collision on a busy road was allegedly held up at knifepoint by two men who fled with his Nissan Skyline.

The Nissan driver, James, spoke to 3AW Fairfax Radio on Thursday morning about the bizarre incident that happened on the Western Ring Road, near Laverton North, just after 6am.

He said he was driving along the road when he spotted a minor collision ahead between a truck and a red Holden Commodore.

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He pulled his car over and went to check on the welfare of those involved, when they allegedly “turned on” him, demanding his keys and pulling out a knife, making threats to stab him before stealing his car, he said.

Victoria Police said the pair assaulted the Nissan owner, and while fleeing with the stolen vehicle, clipped the truck driver who was thankfully uninjured.

A second male truck driver who witnessed the incident also spoke to the Melbourne-based radio station, saying the Nissan sped off towards the West Gate Bridge.

“I’ve seen a bloke running from the crashed car, jump into a white Skyline and they booted it and they aimed the car straight at the driver and I’m pretty sure they hit him,” he told 3AW.

James told 3AW that the two men from the Commodore were driving beside him before the crash, and requested he pulled over, saying there was an issue with his vehicle.

The stolen Skyline was believed to be registered with the plates, 1AI 2BX.

Police said they did not believe this was a road rage incident.

Anyone with information should phone Crime Stoppers on 1800 333 000.

Car hijacking Western Ring Road #Laverton North @theheraldsun pic.twitter.com/7BfK6IpswS

— Nicole Garmston (@garmoheraldsun) January 27, 2016