Chinese shares plunged more than five percent within an hour of mainland markets opening Tuesday, extending falls that have put them into bear territory despite a surprise interest rate cut at the weekend.

The benchmark Shanghai Composite Index slumped 5.03 percent, or 203.97 points, to 3,849.06. The Shenzhen Composite Index, which tracks stocks on China's second exchange, tumbled 6.33 percent, or 148.92 points, to 2,202.48.