Most of the companies say the decision was made as major shareholders increased holdings and company leaders came up with measures to stabilize stock prices under the central government's series of prop-up measures.

　　In the meantime, China's securities regulator has issued a statement, vowing to strictly crack down on illicit securities trading.

　　中国打击非法证券交易行为

　　The China Securities Regulatory Commission says it will standardize securities accounts after finding some agencies and individuals set up virtual accounts or traded with borrowed accounts.

　　The commission also urged local authorities to verify the authenticity of securities accounts and be more strict when supervising them.

　　The move is believed to target illicit financing.

　　The securities regulator also urged brokers to standardize external access to information systems.

　　Also, the Public Security Ministry is said to have found clues that certain trading firms have allegedly manipulated futures trading in the stock market.

　　The investigation, started on last Thursday, is being led by Vice Minister of Public Security Meng Qingfeng.

　　The investigation team visited the head office of the China Securities Regulatory Commission on Thursday to investigate what it called "malicious short-selling of stocks and stock indices".

　　Short selling is believed to be part of the reason for the stock market nosedive over the past few weeks.

　　The team arrived in Shanghai on Friday to search for further clues on such illegal practices.

　　For CRI, I'm Niu Honglin.