BEIJING--A closely watched gauge of China's manufacturing activities showed sluggish growth for a second straight month, indicating that the world's second-largest economy still faces downward pressure.

Uncertainties have been hovering over the Chinese economy as recent economic data ranging from industrial production and energy consumption to fixed-asset investment point to further weakness. Many economists believe they show the Chinese economy stumbled in the third quarter after a slight rebound in the second quarter. Beijing has refrained from using massive stimulus measures to prop up growth.

The HSBC China Manufacturing Purchasing Managers' Index, a measure of nationwide manufacturing activity, was unchanged from August at a final reading of 50.2 in September, HSBC Holdings PLC and data provider Markit said Tuesday. The final reading was slightly lower than HSBC's preliminary September PMI of 50.5, announced last week.

A reading below 50 indicates a contraction in manufacturing activity from the previous month, whereas a reading above that indicates expansion.

"The data in September suggest that manufacturing activity continues to expand at a slow pace," said HSBC China Chief Economist Qu Hongbin. "We think risks to growth are still on the downside and warrant more accommodative monetary as well as fiscal policies."

Mr. Qu said the subindexes for output and new orders were both revised down in the final reading, while the new export-orders subindex rose to its highest reading since March 2010 thanks to stronger demand from abroad.

Zhang Fan, an economist at CIMB, said the HSBC PMI showed that Chinese domestic growth momentum remained weak in September and will drag down economic growth in the third quarter.

Exports were the main bright spot in the PMI reading, helping to compensate for sagging domestic demand, Mr. Zhang said.

China's economy grew 7.4% in the first quarter and then rebounded slightly to 7.5% in the second, but both were well below last year's 7.7% growth rate. China is scheduled to report the third quarter's gross domestic product on Oct. 21.

"Beijing needs more targeted easing measures on both monetary and fiscal fronts to keep the growth from further deceleration," said Mr. Zhang.

Economists have been worrying that China may miss its annual growth target of 7.5% this year for the first time since the Asian financial crisis, but policy makers have publicly ruled out another massive stimulus program like the one launched during the global financial crisis. That program saw China safely through the global downturn but left a legacy of bad debt and led to overcapacity problems in many industries.

China's leaders have said a growth rate "slightly higher or lower" than the target is acceptable as long as the economy generates enough jobs. However, the continued slowdown in growth may eventually endanger that goal.

HSBC said that "companies continued to cut their staffing levels in September at a modest pace" despite higher volumes of new work. China's official urban unemployment rate has been stuck at a level of around 4% for years, but that gauge is widely regarded as an unreliable measure. A sharp decline in employment could raise alarm bells and prompt the government to take more aggressive actions, analysts said.

China's government has so far stuck with what they call targeted easing measures to keep growth on track. In the latest move, the People's Bank of China earlier this month injected a total of 500 billion yuan ($80.6 billion) liquidity into the country's top four state-owned banks, in a bid to keep borrowing costs down and support sluggish economic growth.

Grace Zhu