China's manufacturing activity continued to struggle in August as orders from overseas declined at their sharpest rate since March 2009.

The flash China manufacturing purchase manager index (PMI) hit a nine-month low at 47.8 this month, down from 49.3 in July, according to figures released by HSBC on Thursday.

Manufacturing output index also retreated to a five-month low at 47.9, compared with 50.9 in July. A reading above 50 suggests expansion, while a reading below 50 indicates contraction.

"Falling orders dragged down the August flash PMI to a nine-month low, suggesting Chinese producers are still struggling with strong global headwinds," said Qu Hongbin, chief economist at HSBC China.

"To achieve the stated policy goal of stabilizing growth and the jobs markets, Beijing must step up policy easing to lift infrastructure investment in the coming months," said Qu, who is also co-head of Asian Economic Research at HSBC.

HSBC's preliminary figure for the Chinese PMI is calculated based on 85 to 90 percent of the total responses collected by the bank between August 13 and 21 for its monthly PMI survey. It is issued about one week before the final PMI reading.

The National Bureau of Statistics and the China Federation of Logistics and Purchasing are due to release official PMI data for August on Sept 1. The official PMI data is based on a survey of purchasing managers in more than 820 companies, in 20 industries.