Switzerland's road agency has imposed a preliminary ban on new registrations of Porsche Cayenne cars equipped with manipulated diesel engine management software, a media report said.

The preliminary ban, imposed on Cayenne SUVs with three-litre diesel motors meeting Euro 6, does not affect cars already registered in Switzerland, the agency told Reuters.

Sports car maker Porsche is owned by Volkswagen which in 2015 admitted to systematic manipulation of engine management software to cheat emissions tests.

Germany in late July announced a recall of affected Porsche Cayenne models after finding potentially illegal emissions controlling software in the vehicles, Reuters noted.

Germany must eventually follow other European countries in banning new diesel cars, Chancellor Angela Merkel has said, conceding for the first time that diesel's days are numbered in the wake of the emissions scandals. Her comments followed mounting pressure on Germany's automakers who concealed from regulators the true emissions level of diesel vehicles, the Reuters report added.