Chinese shares plunged in morning trading Monday, extended losses from the past two weeks despite a surprise interest rate cut at the weekend.

The benchmark Shanghai Composite Index dived 3.75 percent, or 157.39 points, to 4035.48 by midday, while the Shenzhen Composite Index, which tracks stocks on China's second exchange, tumbled 5.93 percent, or 148.46 points, to 2,354.50.