Chinese manufacturing contracted for the second month in a row in September amid a slowdown in the world's No. 2 economy.

An official manufacturing index based on a survey of factory purchasing managers edged up to 49.8 in September from August's 49.7, which was the lowest level since August 2012. In July, it was 50.0.

The index, compiled by the Chinese Federation for Logistics and Purchasing, is based on a 100-point scale on which numbers above 50 indicate expansion.

China's economic growth held steady at 7 percent in the latest quarter ending in June, which was the weakest performance since the 2008 global crisis. Officials hope to maintain the growth rate for the rest of the year but many economists doubt the target will be met.