China's factory activity unexpectedly shrank in October after resuming expansion for the first time in half a year in September, official data showed on Tuesday.

China's official purchasing managers index for the manufacturing sectorfell to 49.5 in October from 50.2 in September, below the 50-point mark that separates contraction from growth, the National Bureau of Statistics said on Tuesday.

"The level of economic prosperity has fallen in China, and the foundation for continued recovery still needs consolidation," Zhao Qinghe, an NBS statistician, said in a statement posted on the bureau's website.

The sub-index for production came in at 50.9 in October from 52.7 in September, while the gauge for new orders declined to 49.5 in October from 50.5 in September, the NBS said.

China's non-manufacturing PMI came in at 50.6 in October, down from 51.7 a month earlier. Also, the country's official composite PMI, which includes both manufacturing and non-manufacturing activities, came in at 50.7 in October compared with 52 in September, according to the NBS.