VW US chief steps down amid emission scandal

Horn, who joined VW in 1990 and became chief executive of Volkswagen Group of America in January 2014, will leave "effective immediately" by mutual agreement with the company, the automaker said.

"'I want personally to say 'thank you' to Michael Horn for the great work he has done for the brand and with the dealers in the United States," said Herbert Diess, chief executive of the Volkswagen Passenger Cars brand.

"Michael Horn built up a strong relationship with our national dealer body and showed exemplary leadership during difficult times for the brand."

Volkswagen has admitted that its Volkswagen, Audi and Porsche diesels marketed as environmentally friendly were equipped secretly with illegal devices that hid above-regulation pollution levels from regulators.

Volkswagen is facing multiple investigations in the United States and other countries regarding the cheating, which affected some 600,000 vehicles in the United States and more than 11 million worldwide.

The company is facing potentially tens of billions of dollars in fines and owner compensation.

Horn made headlines last September shortly after the VW emissions-cheating scandal broke, saying at vehicle launch event that the company "totally screwed up" and acknowledging that it likely would suffer big financial penalties due to the scandal.