Growth in China's fixed-asset investment, one of the crucial drivers of the economy, slowed to 10.9 percent in the first eight months of 2015 - the weakest pace in nearly 15 years, data from the National Bureau of Statistics showed on Sunday.
Analysts polled by Reuters had forecast an 11.1 percent rise, compared with 11.2 percent in January-July.
Factory output also was weaker than expected, rising 6.1 percent in August from a year earlier. Markets had expected a 6.4 percent increase, compared with July's 6.0 percent.
Property continues to drag
Annual growth in China's real estate investment also continued to cool, slowing to 3.5 percent in the first eight months, the weakest since early 2009, from 4.3 percent in January-July.
While home sales and prices are slowly recovering from a slump last year - the area of property sold rose at a slightly faster pace of 7.2 percent in January-August - analysts say it will take time for developers to work off a huge overhang of unsold houses and a sharp falloff in new construction will continue to dampen demand for materials from cement to steel.
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Sales of earth excavators fell 33 percent in August from a year earlier, hitting heavy machinery makers such as China's Sany and U.S. heavyweight Caterpillar Inc., Bank of America Merrill Lynch said in a note last week.
"The property sector is the biggest drag on China's economy," said Yu Pingkang, chief economist at Huatai Securities in Shenzhen.
"A pick-up in infrastructure investment is insufficient to offset the slowdown in property investment." Yu has pencilled in 6.9 percent growth for the third quarter.
Retail sales were the lone positive surprise, growing 10.8 percent in August from a year earlier, above forecasts of 10.5 percent, the same as July.
But the increase did not appear to jibe with recent reports from local and foreign firms in China of slowing sales.
Chinese e-commerce giant Alibaba Group Holding Ltd., which dominates online sales in the country, on Tuesday lowered its sales forecasts in a fresh signal that the economic slowdown is taking a bite out of consumer spending.
Vehicle sales fell 3 percent in August from a year earlier, the China Association of Automobile Manufacturers said.
Data last week showed that China's manufacturers slashed prices at the fastest rate in six years in August as commodity prices fell and demand cooled, signalling stubborn deflationary risks in the economy and adding to expectations of further stimulus measures.
Imports tumbled more than expected while exports shrank again, pointing to persistently weak demand both at home and abroad.
China's surprise yuan devaluation last month and a plunge in its stock markets since June have fuelled fears of more shocks to the economy, although Premier Li Keqiang last week brushed off concerns it was facing a hard landing.
Most analysts agree the economy is likely facing a prolonged but gradual slowdown, rather than a sharp loss of momentum.
China's central bank has cut interest rate five times since November and repeatedly relaxed banks' reserve requirements (RRR) in a bid to put a floor beneath the sputtering economy.
Further policy easing is widely expected in coming months, and the government is also trying to boost investment in infrastructure projects to support growth.
The government is aiming for annual economic growth of around 7 percent this year, which would the slowest in half a quarter century.