BEIJING?- China's value-added industrial output was down in September, partly due to a slowdown in the country's mining and energy sectors, data from the National Bureau of Statistics (NBS) showed on Monday.

China's value-added industrial output expanded 5.7 percent year on year in September, down from 6.1 percent in August, according to the NBS.Year-on-year growth in the first three quarters stood at 6.2 percent, slightly down from 6.3 percent in the first eight months.

Manufacturing output expanded 6.7 percent, down from 6.8 percent in August. Mining output dropped sharply from 4-percent growth in August to rise 1.2 percent, while output of the electricity, heating, gas and water sectors increased 0.7 percent, down from 1.2 percent last month, the bureau said.

Slower growth of State-owned enterprises (SOE) also dragged down the data. In September, industrial output generated by SOEs shrank 1.4 percent, sharply down from the 1.3-percent growth registered in the Jan to Sept period.

The industrial output data also came with the release of gross domestic product (GDP) data in the first three quarters, which expanded 6.9 percent to hit 48.78 trillion yuan ($7.68 trillion).

The data showed a slowdown from the 7-percent growth in the first two quarters, mainly due to structural changes in the domestic market and slower economic growth around the world, said NBS spokesperson Sheng Laiyun.

The country's industrial sector is still battling overcapacity, which will continue to put downward pressure on the field in the short term, said Sheng.

Monday's data also showed that industrial output in China's western areas rose 8 percent in September year on year, trailed by 7.8 percent in central regions and 6 percent in eastern regions. Industrial output in the northeastern areas dropped 1.8 percent.

China uses value-added industrial output to measure the final value of industrial production, or the value of gross industrial output minus intermediate input, such as raw materials and labor costs.

The NBS data only tracks the output of large Chinese companies with annual primary business revenues of more than 20 million yuan ($3.15 million).