Volkswagen's luxury diesel cars in Europe are fitted with the same software that American regulators say was used to cheat emissions tests in the United States, the carmaker said on Thursday. U.S. regulators said on Monday that about 10,000 VW cars in the United States - including some Audi and Porsche models - were equipped with auxiliary emission control devices (AECD) that masked the fact that the cars could emit up to nine times the allowed amount of smog-causing nitrogen oxide. They said the firm had failed to inform them such devices was fitted in large 3.0 litre engines used in luxury sport utility vehicles. This widened the VW scandal, which had previously focused mainly on smaller-engined mass-market cars. Volkswagen, which has denied the AECD software altered emission levels "in a forbidden way", told Reuters on Thursday that the same devices were installed in cars in Europe - its biggest market, accounting for around 40 percent of group sales.