Some analysts said another reason for the fall of nearly all the Chinese stocks and ETFs could be anticipation of Alibaba's IPO as traders made room in their portfolio for the new stock, although Oey did not think the listing of one firm would significantly affect overall market performance.
Saturday's reports, combined with other recent indicators, signaled a dramatic slowdown in the world's second-largest economy. China's factory output for August grew at the lowest pace in nearly six years, while other indicators such as retail sales and fixed-asset investment increased much less than expected.
"The economy over there is weaker than other people expected," Henry Guo, managing director and equity research analyst at JG Capital, said. "This is just a time for correction. I'm not worried about it."
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But he also pointed to losses in the Nasdaq on Monday as the index fell more than 1 percent to 4,518.90 in the close. Twitter fell 5 percent and Facebook lost nearly 4 percent in Monday trading, while Apple edged only slightly lower.
China Petroleum and Chemical fell more than 6 percent on Monday, while Sinopec Shanghai Petrochemical fell nearly 4 percent. Real estate listing website SouFun lost 4.9 percent. Search engine Baidu lost 3.3 percent, and video-sharing website Youku fell almost 4 percent. Chinese tech conglomerate Sina lost nearly 5 percent, while its subsidiary and China's Twitter-like service Weibo fell 11.6 percent. Last Thursday, Weibo had rallied more than 16 percent.
Chinese exchange-traded funds also fell, with PowerShares Golden Dragon China Portfolio losing 2.9 percent, and iShares China Large-Cap falling 1.4 percent, among other fund losses.
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In Asia, the weak data had sent most local stocks lower, but the Shanghai Stock Exchange reversed to close up 0.31 percent on Monday.
—By CNBC's Evelyn Cheng