China has unveiled a slew of “confessions” from brokers and journalists as authorities struggled to contain the biggest stock market sell-off since 2008.

The pre-trial confessions – common in high-profile cases in China – suggest that Beijing intends to make a public example of the alleged transgressors.

The London-listed FTSE 250 hedge fund manager Man Group was also dragged into the affair on Monday as it emerged that Li Yifei, the chairman of its China unit, was taken into custody to assist a police inquiry into market volatility. Man declined to comment on Ms Li, one of the nation’s leading businesswomen and the former head of MTV in China.

China’s main Shanghai stock market fell 0.8 per cent on Monday, marking a 12 per cent fall for August and a near 40 per cent fall from the end of June. Coming after a 14 per cent slump in July, it is the biggest two-month fall since 2008. The shock waves from China – fuelled by fears over a hard landing for the previously fast-growing economy – reverberated around the world last month, wiping more than $5 trillion (£3.2 trillion) off the value of global stock markets as Beijing also unveiled a shock devaluation of its currency.

Authorities in China are cracking down on trading abuses and malicious short selling – betting against shares – as well as intervening in markets directly in an attempt to calm turmoil before Thursday’s celebration of the 70th anniversary of its victory against Japan in the Second World War.

Xinhua said Wang Xiaolu, a reporter at the Caijing business magazine, had confessed to writing about the Chinese stock market “based on hearsay and his own subjective guesses” that “inflicted huge losses on the country and investors”. Caijing said it had not been given a reason for his detention.

Liu Shufan, an official with the China Securities Regulatory Commission (CSRC), confessed to crimes including insider trading, using his position to boost a listed company’s share price in return for bribes. Xinhua added that Citic executives Xu Gang, Liu Wei, Fang Qingli and Chen Rongjie had confessed to insider trading, although Citic declined to comment.