UPDATE 1-German car market falls unadjusted 10 pct in Aug

(Adds detail, quotes, background)

FRANKFURT, Sept 2 (Reuters) - German car registrations fell an unadjusted 10.4 percent in August, due to two fewer working days, only the third monthly decline this year, masking otherwise stable underlying demand in Europe's largest economy.

Official data published by the German motor vehicle department KBA showed registrations of new passenger cars fell to 214,386 vehicles last month, bringing the cumulative total for the first eight months to 2.11 million, a total rise of 1.7 percent.

While significantly better than the performance in other western European countries such as Italy and Spain, the slight increase in year-to-date registrations was helped by a flattering comparison with last year, the German car market's worst year since reunification in late 1990.

"The domestic passenger car market could not extricate itself in August from the weak economic conditions distinguished by consumer restraint," German automotive industry association VDA said in a statement, singling out in particular the "enormous costs at the pump".

Volker Lange, president of rival lobbying group VDIK, which represents foreign carmakers in Germany, added in a statement: "The decline in real net wages per capita is having a considerable effect on private car purchases."

Both groups called on the German government to help support the industry by aiding consumers to buy newer, more fuel-efficient cars.

The KBA said it registered new passenger cars fulfilling the strictest Euro 5 norms for the first time, but at just 610 vehicles they remained a small fraction relative to the 93 percent that met Euro 4 and the 6 percent that could only manage Euro 3.

Average carbon dioxide emissions of the newly registered vehicles edged down to 163 grams per kilometre versus an average of 166 g/km for the first six months. "The trend to smaller, more fuel-efficient cars was substantiated by the registrations in August," the KBA said.

On Monday, Italy reported new car sales fell 26 percent in August, while Spain suffered a 41 percent plunge. Despite a government incentive scheme, France watched its new car market slide 7.1 percent.

The weakness contrasts sharply with the boom in car demand in Russia, where growth already outpaces Western European markets, and which is expected to overtake the German car market in volume terms next year at the latest. (Reporting by Christiaan Hetzner, editing by Will Waterman)