UPDATE: Police arrest alleged carjacker following 200km pursuit

Police have arrested a man who allegedly led them on a four-hour high-speed pursuit through rural Victoria after carjacking a woman at gunpoint today.

The armed man reportedly crashed a stolen car in Dandenong and then forced a 52-year-old woman from her vehicle before driving off.

Police pursued the driver down the Princes Highway near Drouin, eventually stopping the car and arresting the man at Swan Reach, about 270km away from where the pursuit started.

They surrounded the alleged carjacker's vehicle before taking the man into custody.

Witnesses told Fairfax Radio the man drove along the freeway and through country towns at speeds up to 160km/h.

One 3AW listener told presenter Denis Walter a woman had been "booted from the car" in Morwell and that she was "clearly distressed".

Bairnsdale resident Matt Weatherall said the car sped past him at high speed and collided with a firetruck in the process.

"It was over in a flash," he told 9news.com.au.

He said the vehicle was being pursued by one marked police car and three Special Operations Group 4WDs.

The driver crashed the second car in Tullock Way in Traralgon before stealing a brown Jeep at gunpoint.