China's non-manufacturing purchasing managers' index (PMI) fell to 53.9 percent in August from 54.1 percent for July, according to official data released on Tuesday.

A PMI reading of more than 50 percent indicates expansion in non-manufacturing activity, while a reading below 50 percent indicates contraction. The index was released by the National Bureau of Statistics (NBS) and the China Federation of Logistics and Purchasing.

The non-manufacturing PMI covers sectors including service, construction, software, aviation, railway transport and real estate.

In August, the construction sector showed modest improvement but service industry weakened compared with a month ago, the NBS said.

The sub-index for new orders rose to 50.9 percent last month from 50.3 percent in July while that for employment gained 1.2 percentage points to 52.5 percent.

The data was issued after the NBS announced on Sunday that its manufacturing PMI climbed to 51 percent in August from July's 50.3 percent.