The final HSBC/Markit PMI reading for September is scheduled for release on Sept 30. A separate manufacturing index from the National Bureau of Statistics and China Federation of Logistics and Purchasing will be published on Oct 1. That figure fell to 51.1 in August from 51.7 in July.

Tuesday's report, known as the Flash PMI, is typically based on 85 percent to 90 percent of responses to surveys sent to purchasing managers at more than 420 companies.

Estimates from 21 analysts ranged from 48.5 to 50.5, while the median was 50. Numbers above 50 indicate expansion.

A separate report showed China's economy remained stuck in "low gear" this quarter.

The China Beige Book showed growth in investment slowed further, borrowing costs rose, and the share of firms applying for and getting bank loans remained at "rock bottom levels".

In contrast, hiring picked up, and corporate profit margins improved, suggesting widespread government efforts to reignite growth are unlikely, it said.

Leland Miller, China Beige Book International president, said in a statement with Craig Charney, research and polling director: "The absence of deteriorating conditions for most firms, both in terms of hiring and margins, does much to explain Beijing's reluctance to introduce more large-scale stimulus."

China will maintain a "steady and prudent" monetary policy stance, Ma Jun, the chief economist for the research bureau of the People's Bank of China, wrote in a commentary last week in Financial News, which is published by the central bank.

Strong stimulus measures are not needed because China is shifting its focus to employment from gross domestic product, and monetary-policy easing will increase economic and financial risks, Ma said.

China Sept factory activity edges up on stronger orders	PMI shows emphasis shifting