BEIJING, (Xinhua) - Chinese shares tumbled Wednesday morning after a three-day gaining streak, as domestic investors remained cautious amid increasing global uncertainties.

Major stock indices tumbled on opening, and the benchmark Shanghai Composite Index further went down 1.87 percent to 2,774.78 at midday. The Shenzhen Component Index lost 2.2 percent to end at 9,003.

Excluding stocks in suspension, most of the 3,000-plus companies listed on the Shanghai and Shenzhen stock exchanges saw falling share prices.

Textile machinery, ship making and electronic information led the declines. Coal mining, oil exploration and environmental sectors also suffered.

The ChiNext Index, tracking China's NASDAQ-style enterprises, shed 2.24 percent to 1,557.27.