Russian car sales suffered a double-digit percentage drop in May, a business lobby that groups Europe's top auto makers said on Monday, prompting it to slash its forecast for the full year to a decline of 5 percent.

The downbeat figures published by the Association of European Businesses (AEB) provided one of the first indications that the slowdown in Russia's $2 trillion economy - Europe's second-largest car market - intensified last month.

The AEB cut its forecast for 2013 to 2.8 million units following three months of falling sales as economic growth in Russia slowed.

That will be lower than the 2.94 million recorded in 2012. The AEB had previously forecast that 2013 car sales would be flat on the previous year.

"Market participants are concerned about this situation, and expect continued slow demand before a potential improvement in the second half of the year," said Joerg Schreiber, Chairman of the AEB Automobile Manufacturers Committee in a statement.

For May, sales fell 12 percent year-on-year to 230,000 units. The fall was heavier than the 8 percent decrease seen in April and the 4 percent fall in March.

President Vladimir Putin said earlier on Monday that the country's weakening economic growth was a cause for concern.

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