His predecessor Trevor Hill, who currently works at the German headquarters, and Park Dong-hoon, who headed AVK's Volkswagen division from 2005 to 2013, also face similar charges. Park now heads Renault Samsung Motors Co.

During the first preparatory hearing held at the Seoul Central District Court, Thammer's legal representative said he was not aware that the cars implicated in the scandal did not meet the local emissions standard.

Park's attorney also denied the allegations, saying the former executive is not even well aware of what prosecutors have laid out as factual relations.

Prosecutors suspect that the defendants imported some 120,000 vehicles in 15 models, whose emissions systems were manipulated, from 2008 to 2015.

The automaker is also accused of fabricating reports to get approval from the local government. Prosecutors said such irregularities took place from as early as August 2010 to January 2015.

One of its executives -- who was in charge of the vehicle certification process, identified only by his surname Yoon -- was first indicted in July and received a jail term of one year and a half from the court in January. He is standing trial with the other executives after prosecutors additionally charged him.

The next preparatory hearing is slated for May 24. (Yonhap)