The purchasing managers' index (PMI) for China's manufacturing sector came in at 49.6 in September, edging down from 50.1 in August, data from the National Bureau of Statistics (NBS) showed Thursday.

A reading above 50 indicates expansion, while a reading below reflects contraction.

The slowdown came as factory activities in energy-intensive sectors slackened, weighing on the overall performance of the manufacturing industry, according to the NBS.

The sub-index for production stood at 49.5 in September, retreating 1.4 percentage points from a month earlier, while that for new orders dropped 0.3 percentage points to 49.3.

The new export order and import sub-indexes edged down to 46.2 and 46.8, respectively.

Thursday's data also showed that the PMI for China's non-manufacturing sector came in at 53.2 in September, up from 47.5 in August.