The Shanghai Composite Index was down 0.78 percent, or 15.62 points, to 1,999.11 in afternoon trading, breaking through the 2,000 point level that dealers had pegged as support.

The benchmark index last fell to a more-than-three-year low of 1,999.48 points on September 26 this year.

"It's difficult for the index to stay above the 2,000 point level because of a lack of substantial pro-market policies at the moment," BOC International analyst Shen Jun told AFP.

"There are also uncertainties in both the domestic and global economies," he added.