Volkswagen unit Audi will launch clean diesel engine cars in Japan in the near future, officials have said.

Clean diesel engine technologies are essential for for the automaker to achieve its target of doubling annual sales in Japan to 40,000 units by 2015 from 2011 levels, an Audi executive told Jiji Press.

Audi will launch hybrid luxury sedans in Japan later this year and the addition of clean diesel models will expand the firm’s lineup of environmentally friendly vehicles, officials said.

Clean diesel engines are beginning to attract attention in Japan after Mazda Motor put its CX-5 SUV on sale in February with a new line of efficient petrol and diesel engines and automatic transmission.

Audi officials have not said when clean diesel models will be launched in Japan. But an executive in charge of marketing told Jiji the automaker cannot wait very long, apparently taking into consideration rival BMW’s plan to release clean diesel cars in Japan this spring.

Audi originally planned to launch clean diesel engine cars in Japan in 2010 but postponed the move because petrol-electric hybrids are the mainstream in the country’s eco-friendly vehicle market.