BEIJING -- China's manufacturing activities rose to a six-month high in September, according to a preliminary survey from HSBC.

The HSBC Flash Manufacturing Purchasing Managers' Index for September rose to 51.2, the highest level since April and up from 50.1 in August, according to figures released by HSBC on Monday.

The Flash PMI is based on a survey of purchasing executives in Chinese companies. An index figure above 50 signals expansion, while below 50 indicates contraction.

Qu Hongbin, chief economist of HSBC China, said the country's manufacturing sectors are being boosted by rising external demand and micro stimulus policies at home.

The HSBC report showed that output and new orders including new export orders rose in September. Meanwhile, stocks of raw material purchases and finished goods also increased.

That suggested restocking is part of the driver of the current economic recovery, according to Xiaojia Zhi and Ting Lu, China economists from Bank of America Merrill Lynch, in a report.

The Flash PMI is published on a monthly basis, approximately one week before final PMI data are released, making the HSBC PMI the earliest available indicator of manufacturing sector operating conditions in China.