BEIJING -- China's stock index futures all turned sharply higher on Friday after the country's top economic planner unveiled stimulus plans worth more than 1 trillion yuan ($157.7 billion) to buoy the slowing economy.

The contract for September, the most actively traded, surged 5.22 percent from the previous trading day to 2,341.2 points.

The October contract soared 5.17 percent to close at 2,355.2 points. The December contract jumped 5.08 percent to 2,380 points, while the March 2013 contract shot up 5.18 percent to finish at 2,414 points.

The stock-index contracts, agreements to buy or sell the Hushen 300 Index at a preset value on an agreed date, are designed to allow investors to bet on and profit from both gains and declines in the market.

The index futures was launched at the China Financial Futures Exchange and started trading from April 16, 2010. The CFFEX has set the base value for all the four contracts at 3,399 points.