China, Hong Kong stocks tumble, joining global selloff on slowdown fears

Passersby are reflected on a screen displaying stock quotation, the stock market indices of various countries (bottom R) and exchange rates (top R) at a brokerage in Tokyo, Japan, September 29, 2015. Asian shares skidded to 3-1/2-year lows and the dollar sagged on Tuesday, pulled down by a sharp losses on Wall Street after weak Chinese data rekindled worries about its fragile economy. REUTERS/

Commodity-related companies were under particularly fierce pressure as worries over sagging demand sent prices of metal and crude oil skidding overnight.

China's blue-chip CSI300 index and the flagship Shanghai Composite Index both lost nearly 2 percent by midday, ending the morning session at 3,181.50 points and 3,043.85, respectively