Shanghai stocks tumbled 6.41 percent at the opening on Tuesday, extending the previous day's plunge on mounting worries over China's faltering economy and its impact on global growth, dealers said.

China's benchmark Shanghai Composite Index lost 205.78 points to 3,004.13. The Shenzhen Composite Index, which tracks stocks on China's second exchange, dropped 6.97 percent, or 131.18 points, to 1,751.28.