The move will affect vehicles imported from Aug. 17. Vehicles already registered in Switzerland may continue to operate, but must be retrofitted, Astra said in a statement.

Mercedes Vitos with 1.6-litre diesel engines, Porsche Macans with 3-litre diesel engines and Cayennes with 4.2-litre diesel engine are affected by the action. All have Euro 6 emission norms, which refers to the emissions standards these engines are required to meet.

Daimler said it had stopped exporting the Vito model after German authorities in May ordered a recall and halt to new registrations for the vehicle. This affected 24 Vito vehicles destined for Switzerland, a spokesman for the German manufacturer said in an emailed statement.

(Reporting by Michael Shields; Editing by Elaine Hardcastle and Jane Merriman)