Audi has said 2.1 million of its cars worldwide were fitted with the software that allowed parent Volkswagen to cheat US emission tests.
Some 1.42 million Audi vehicles with so-called EU5 engines are affected in western Europe, with 577,000 in Germany, and almost 13,000 in the US.
Affected models include the A1, A3, A4, A5, A6, TT, Q3 and Q5, a spokesman told the Reuters news agency
VW said last week that 11 million cars within the group could be affected.
The scandal was revealed after the US Environmental Protection Agency found that some diesel cars were fitted with devices that could detect when the engine was being tested and could change the car's performance to improve results.