BEIJING, Aug 1 (Reuters) - Activity in China's manufacturing sector unexpectedly shrank slightly in July from the previous month, an official survey showed on Monday.

The official Purchasing Managers' Index (PMI) stood at 49.9 in July, compared with the previous month's reading of 50 and just below the 50-point mark that separates growth from contraction on a monthly basis.

Analysts polled by Reuters predicted a reading of 50.0.

(Reporting by Sue-Lin Wong; Editing by Kim Coghill)