China's manufacturing activities, measured by the official Purchasing Managers' Index, softened in October after two consecutive months of expansion, according to the National Bureau of Statistics on Tuesday.

The PMI, a gauge of factory conditions, stood at 51.6 in October, the NBS said in a statement on its website. It was 52.4 in September, which marked a five-year high.

A reading above 50 is considered expansion while one below that mark indicates contraction.

The manufacturing sectors of the world's second-largest economy remained on track for expansion since the October reading was above the demarcation mark of 50, said Zhao Qinghe, a senior statistician of the NBS, in a statement.

The week-long National Day holiday in early October had affected production and the growth of new orders, and activities in the energy and pollution-intensive industries have also slowed due to the country's crackdown on pollution in some regions, Zhao said.

China registered a year-on-year GDP growth of 6.8 percent in the third quarter, with growth in the first three quarters coming in at 6.9 percent. Analysts predicted that the economy could slightly weaken in the last quarter of this year, but will probably maintain stable growth momentum.