China's industrial value-added output growth slowed to 13.3 percent year on year in September from 13.9 percent in August, the National Bureau of Statistics (NBS) announced Thursday.

The growth rate for the first nine months was 16.3 percent year on year, down 0.3 percentage points from the January-July period, said NBS spokesman Sheng Laiyun.

For the third quarter alone, year-on-year growth stood at 13.5 percent, he said, compared with a 19.6 percent growth in the first quarter and a 15.9 percent in the second quarter.

From January to August, profits of industrial enterprises of scale -- referring to enterprises with annual sales revenue exceeding 5 million yuan (735,294 U.S. dollars) each -- surged 55 percent from a year earlier to hit 2.6 trillion yuan, said Sheng.

For heavy industries, industrial value-added output in the first three quarters was up 17.5 percent year on year, and that for light industries climbed 13.6 percent, said Sheng.

Industrial value-added output increased 15.6 percent in China's eastern regions, by 18.9 percent in central areas and by 15.6 percent in western parts of the country.

Industrial value-added output measures the final results of industrial production, which is the value of gross industrial output minus intermediate input such as raw materials and labor.

China's GDP grew 9.6 percent in the third quarter from the same period last year, said the NBS. The growth rate was down from 10.3 percent in the second quarter.

But Sheng said the slowdown in industrial production growth and economic expansion was a result of government macro-control measures and a higher comparison basis, as China's industrial production picked up in the second half of 2009.

The discrepancy between the quarterly figures was "narrowing," Sheng added, citing figures of the previous quarters.

Local governments in China had taken greater steps to cut energy consumption and reduce emissions this year, which largely curbed the growth of high energy-consuming industries, he said.

China's six high energy-consuming industries -- iron and steel, nonferrous metals, oil refining, chemicals and electricity generation, and building materials -- saw industrial value-added output up 10.5 percent in the third quarter, according to the NBS.

In the second quarter, industrial value-added output of the six industries grew by 15.1 percent from a year earlier.