The Swiss Federal Roads Office (FEDRO) said Friday registrations of the luxury sport utility vehicles produced by the VW subsidiary would be halted. It said there was a need "to protect the environment."

"The vehicles that are affected by the manipulations will only be allowed for registration as new cars in Switzerland once they conform to regulations," the office said in its announcement.

The preliminary ban does not affect cars already registered in Switzerland.

The 3-liter Porsche Cayenne models had been marketed as conforming to the Euro 6 standard, the lowest EU emissions class for diesel engines.

Illegal emissions-cheating software had been found in Porsche's Cayenne Diesel 3.0 TDI model, German Transport Minister Alexander Dobrindt said in late July. This had allowed the cars to pass tests while exceeding limits in normal driving conditions.  It meant 22,000 vehicles would have to be recalled.

In 2015, Porsche discontinued sales of its Cayenne diesel vehicles to US and Canadian markets as it admitted to systematic manipulation of engine management software to cheat emissions tests.

jm/sms (Reuters, dpa)