China's benchmark Shanghai stock index slid into negative territory in early afternoon on Monday, falling 0.55 percent despite unprecedented government measures to shore up the plunging market.

The Shanghai Composite Index lost 20.32 points to 3,666.60. The market surged 7.82 percent at the open after the government over the weekend unveiled its biggest package of measures to arrest the market slide, including stabilisation funds and a halt to new share offers.