A man has been hospitalised with serious injuries after a tractor tipped on to a motorway from a bridge following a crash.

Kent police said they were called to reports of a single-vehicle collision on the A227 overbridge near Wrotham at 11.17am on Monday. A tractor became separated from its trailer before falling on to the central reservation between junctions 2 and 3 of the M20.

Police earlier believed two vehicles were involved in the collision. They have called for witnesses and anyone with dashcam footage of the collision to come forward.

The man’s next of kin are aware of the incident and he remains in a critical but stable condition in hospital. Kent fire and rescue service and south east coast ambulance service also attended the incident, and remain at the scene, the force said.

The M20 and the A227 remain closed while emergency services deal with the incident, with motorists advised to use alternative routes. Images and footage shared on social media showed a tractor upside down with railings bent in the central reservation.

Large queues of vehicles were forming on either side of the bridge. South east coast ambulance service said it was called to reports of a collision involving a tractor and a lorry on the bridge at about 11.20am.

Multiple crews, a critical care paramedic and the local air ambulance were sent to the scene. The driver of the tractor was airlifted to King’s College hospital in London, the service said.

National Highways said the M20 was expected to be closed in both directions between junctions 1 and 3 into Monday evening for emergency repairs and resurfacing, after damaged caused from the collision and a subsequent fuel spillage.

Anyone with relevant information should contact police on the west Kent appeals line on 01622 604100, quoting reference 18-0475.