Stock markets in the Chinese mainland nudged down amid tepid trading on Thursday.

The benchmark Shanghai Composite Index fell under the 2,100 level, sliding 6.24 points or 0.30 percent to 2,098.89 points on Thursday. The Shenzhen Component Index inched down by 17.43 points or 0.23 percent to close at 7,451.04 points.

Combined turnover on the two bourses on Thursday was 158.34 billion yuan ($25.46 billion), slightly down from the previous trading day's 159.15 billion yuan.

Coal, aerospace, lottery, real estate and cement companies as well as insurers led the decline on Thursday. 

Coal firm Shanghai Ace Co fell by 9.97 percent and Ping An Insurance (Group) Co of China dropped by 1.47 percent to 39.60 yuan.

Stocks tied to the integration of Beijing, Tianjin Municipality and Hebei Province and lottery companies, which had seen gains recently, fell back on Thursday. Tangshan Jidong Equipment Engineering Co fell by 8.55 percent to 8.02 yuan.

Meanwhile, there were gains for stocks linked to Ningbo, rural banks and wearable devices.

According to local media reports, Ningbo, a city in East China's Zhejiang Province, is considering developing a free trade zone. The news boosted Ningbo-based companies. Ningbo Marine Company and Ningbo Construction Co jumped by the daily limit of 10 percent to 3.97 yuan and 8.76, respectively.

ChiNext, China's NASDAQ-style board for high-tech and fast-growing start-ups listed in Shenzhen, gained by 8.29 points or 0.61 percent to close at 1,367.59 points on Thursday.