Zhang Yujun is by far the highest-ranked securities official investigated. [CHINA DAILY]

A senior official at China's securities watchdog is being investigated by the nation's top anti-graft body as the crackdown intensifies against illegal activities in the securities market.

Zhang Yujun, the assistant chairman of the China Securities Regulatory Commission, is being investigated for "serious violations of laws and disciplines".

This was announced by the Central Commission for Discipline Inspection of the Communist Party of China in a statement on its website on Wednesday evening.

The announcement comes amid volatility in the stock market, which has suffered a dramatic fall from its peak in mid-June.

Zhang, 52, is by far the highest-ranked securities official to be investigated by the country's anti-corruption watchdog. The commission declined to comment when contacted by China Daily.

Zhang's case follows police investigations into several senior executives from the country's largest securities brokerage, CITIC Securities Co, for alleged insider trading and information leaks.

Analysts said the recent series of investigations highlights Beijing's desire to clean up the securities market and to ensure that market-driven reform of this sector is not derailed by rampant malpractice.

Dong Dengxin, a financial researcher at Wuhan University of Science and Technology, said, "Successful implementation of major reforms, including the registration-based plan for new share sales, relies on an effective regulatory and law enforcement body.

"The latest investigation shows Beijing's desire to improve market supervision and to deter illegal activities."

Zhang joined the commission in 1995 and is known to be an advocate of financial innovation. He was in charge of the regulation of financial institutions, including securities firms, fund management companies and futures brokerages.

He was general manager of the Shanghai Stock Exchange from 2008 to 2012 and headed the Shenzhen Stock Exchange from 2000 to 2008.

Born in Sichuan province, Zhang holds a dual doctoral degree in economics and law.