The incident between two vehicles happened on the A227 near Wrotham just before 11.20am today (August 18).
A tractor subsequently fell onto the central reservation between junction two and three of the M20.
(Image: Matthew Carter)M20 London Road Wrotham crash: Live traffic updates
Kent Police is at the scene alongside Kent Fire and Rescue Service and South East Coast Ambulance Service/
One man has been airlifted to hospital with serious injuries.
A lorry and a tractor had been involved in the crash, according to Inrix traffic.
(Image: Patrick Lohlein/X) Kent Fire & Rescue Service confirmed the incident involved two vehicles and crews had extracted one person.
The road is expected to be closed for four to six hours, the fire service added.
National Highways has urged drivers to allow extra time for their journey if travelling in the area.
This is a breaking news story. More to follow.