BEIJING – The China Securities Regulatory Commission (CSRC) on Friday reported six cases involving operations in violation of transaction rules, ringing warning bells of tougher stock market regulations.

The violations include market manipulation, insider trading, and illegal investment consultation and information disclosure. Six companies in Guangdong, Hubei, Shanxi and Jiangsu provinces and Beijing have received fines, with those responsible persnnel sentenced to fixed terms of imprisonment.

Among them was Guangdong Zhonghengxin, an investment company which was accused of market manipulation by recommending pre-bought stocks on a television program. The operation had affected 552 stocks, or one quarter of the entire A-share market, the largest number of such cases in history.

The report came after Guo Shuqing, China's newly appointed top securities regulator, said in his first public speech that supervision of the country's securities market will focus on cracking down on insider trading.

Further details of these cases and more will be revealed in the future, said the CRSC.