Design flaws in China Everbright Securities' trading system triggered an unexpected huge buy, causing the Shanghai stock market to rise more than 5 percent at noon on Friday, the top securities watchdog said on Sunday.

It was the first extreme and individual case since the establishment of a capital market in China, which raised red flags for the entire securities sector, the China Securities Regulatory Commission said in a statement.

The commission said an initial investigation showed that mistakes in application commands and failures of the payment quota control system led the securities company to send a 23.4 billion yuan ($3.83 billion) order to the Shanghai Stock Exchange and close deals valued at 7.27 billion yuan on Friday.