China's top economic planner said Thursday that auto prices fell slightly in September for a third consecutive month, and were expected continue falling in the fourth quarter.

Prices of cars made in China were down 0.41 percent from August and 0.3 percent from September last year, the National Development and Reform Commission (NDRC) said in a statement on its website.

The figures showed prices of Chinese-made passenger cars fell 0.09 percent from August and 2.56 percent year on year.

Commercial vehicles, including buses and trucks, saw bigger price drops in September, 0.35 percent down from August. But it was 3.02 percent higher than a year earlier, according to the NDRC.

While the prices of buses declined by 0.68 percent from last month, those of trucks went up by 0.12 percent and climbed 5.41 percent year on year.

Prices of imported cars followed the trend on a monthly basis, down 0.2 percent from August after prices for passenger cars dropped 0.02 percent and off-road vehicles 0.39 percent month on month, said the statement.

However, on an annual basis, imported car prices rose 9.62 percent.

The general trend of slight price drops was accompanied by faster auto sales growth in China in September.

Official figures released Tuesday showed China's auto sales rose 16.89 percent from a year earlier to 1.56 million vehicles, compared with 16.14 percent in August.

However, analysts are forecasting a slowdown in months to come as a previous boom in large part fueled by tax breaks and subsidies would fade.

The NDRC's price monitoring center predicted auto prices would continue to fall in the fourth quarter of 2010, but did not give specific reasons.