FRANKFURT - Strong demand in China and Germany last month triggered a double-digit growth rate in group sales volume at Volkswagen that wiped away the last signs of weakness from the start of this year.

Volkswagen's head of sales warned investors, however, not to interpret the figures as a sign that the industry had finally returned to lasting health.

Global passenger car markets have not made a sustained recovery yet, so we are anticipating a particularly difficult and challenging year in 2010, Detlef Wittig said in a statement on Friday.

The VW sales chief had forecast in September group volumes would stagnate at around 6.2 million vehicles both this year and next.

Volkswagen delivered 557,300 vehicles in October across its eight car brands, a rise of 11.1 percent.

Cumulative sales rose for the first time in 2009, gaining 0.6 percent to 5.32 million euros in the first 10 months, thanks to the significant boost last month.

The core VW brand saw October deliveries rise 17 percent to 349,800 vehicles, driven by China, Brazil and Germany.

Its Czech value brand Skoda increased its sales by 33 percent to 65,600 cars, while VW's loss-making Seat brand managed a tiny gain of 1.9 percent to 29,600 cars.

Audi had reported its volumes on Monday, tweaking its sales forecast for this year to 925,000 vehicles. (Reporting by Christiaan Hetzner, Editing by Michael Shields)