A key gauge of China's manufacturing activity has fallen below the boom-or-bust line for the fourth straight month. Sluggish domestic demand is a major factor amid the prolonged slump in the country's real estate market.

The Purchasing Managers' Index for August came in at 49.1. That's down 0.3 points from the previous month.

The National Bureau of Statistics surveyed 3,200 manufacturers in compiling the index. Figures above 50 represent growth while those below indicate contraction.

The gauge for large companies stood at 50.4, but midsize firms were at 48.7, and small enterprises at 46.4.

The readings for non-manufacturers, such as service sector businesses, rose 0.1 point from the previous month to 50.3.