* Audi recalls 400,000 A4 in China, Germany
* Faulty Audi airbags not made by Takata -spokesman
* Audi solved problem, adjusted A4 production last week (Adds more detail on airbag problems and background)
BERLIN, Oct 23 (Reuters) - Audi is recalling 850,000 A4 models worldwide due to airbag problems, with about half of the vehicles affected in the luxury carmaker's two biggest markets of China and Germany.
Faulty software in A4 models delivered after 2012 could prevent front airbags from deploying, a spokesman at Audi's Ingolstadt-based headquarters said on Thursday.
Audi said its faulty airbags are not made by Japan's Takata Corp, which is at the centre of a burgeoning number of recalls over air bags that could spray shrapnel at occupants.
Volkswagen -owned Audi is recalling about 250,000 A4 models in China, its biggest market, and 150,000 in Germany, while giving no regional breakdown for the remaining 450,000 cars.
The airbag problem is caused by a software fault, affecting A4 saloons, station wagons and so-called allroad models.
The world's No. 2 luxury-car maker last week adjusted production of A4 models at its German plants in Ingolstadt and Neckarsulm, adding new software.
U.S. safety regulators on Wednesday expanded the number of Takata-equipped vehicles in the United States that may be affected by recalls to 7.8 million vehicles from 10 carmakers.
News of the recall was published earlier on Thursday by Germany's Auto Motor und Sport magazine. (Reporting by Andreas Cremer; Editing by Jonathan Gould and David Holmes)