SHANGHAI – Sales of passenger cars in China – the world’s biggest auto market – rose 18 percent in August from a year earlier as government subsidies and price cuts by dealers helped spur demand.

Passenger car sales totaled 1.02 million vehicles in August, the Shanghai-based China Passenger Car Association, a private research group, said Tuesday.

The figures dovetail with those released earlier by a government-affiliated research institute showing sales of all vehicles rose nearly 56 percent in August from a year earlier, to 1.21 million vehicles. That contrasted with a 5 percent decline in August sales in the U.S., according to AutoData Corp.

China’s roaring growth in auto sales has slowed in recent months after surging more than 60 percent in March. August’s 18 percent increase compares with a 16 percent year-on-year increase in July and a 21 percent increase in June, according to the association’s figures.

But a government decision to extend subsidies for energy-efficient vehicles, plus sharp price cuts by dealers trying to clear inventory, helped support demand, said Rao Da, head of the association.

“Price cuts by Toyota spurred others to also slash prices,” Rao said in an analysis posted on his blog. He noted that the usual pattern of slower sales during the holiday weeks of August has changed as families increasingly opt to buy cars ahead of the school year.

Global automakers have benefited hugely from China’s fast-growing market.