(Yicai Global) Dec. 18 -- Securities brokers were the biggest gainers this morning as China's mainland stock markets opened lower following two straight days of gains.

The Shanghai Composite Index opened 0.03 percent lower at 3,021.47, while the Shenzhen Component Index fell 0.07 percent at 10,299.05. The ChiNext Price Index, which tracks Shenzhen-listed growth enterprises, slid 0.18 percent to 1,789.49.

Shares in security firms started the day 1 percent higher.