Chinese ADRs and ETFs tumbled in morning trading; YINN tumbles over 28%; Ke holdings and Bilibili sinks over 10%.
The chairman of China's National Development and Reform Commission Zheng Shanjie said he is "fully confident" the country will achieve its full-year economic and social goals.
But he added: "The downward pressures on China's economy is also increasing".
Mr Zheng's comments came as he announced that China will issue 200 billion yuan ($28bn; £21.5bn) for spending and investment projects by the end of this year.
"The market really expected more. The correction will be even stronger if the data on the Golden Week in terms of consumption is weak," said Alicia Garcia-Herrero, chief economist for the Asia Pacific region at investment bank Natixis.
"The market is reacting to the lack of a real fiscal stimulus. I would not have organised a press conference not to announce anything new."