The arrest of a banking tycoon has sparked panic among investors as Vietnam's stock market plunged Thursday for a third-consecutive day in its sharpest fall in nearly four years, according to dpa. Nguyen Duc Kien, co-founder of Asia Commercial Bank, Vietnam's fourth-biggest lender by market value, was arrested Monday and was charged with "illegal business activities," police said, meaning he was accused of doing business in fields in which he was not registered with authorities. The stock market has lost nearly 11 per cent of its value since Monday after gaining 19 per cent since the beginning of the year. "Many traders were still pessimistic because Kien has great influence in several banks," said Pham Trung, a trader at FPT Securities in Hanoi. "The market is suffering from a domino effect as bank stocks are being sold heavily." Kien, 48, faces charges in connection with three companies he owns that have a combined registered capital of 110 million dollars. Kien's companies are not allowed to participate in investments, but they allegedly issued corporate bonds and false business plans to secure hundreds of millions of dollars from banks, the Tuoi Tre newspaper said, citing police. Kien then allegedly used that money to buy shares of many banks and mortgaged the shares at those banks for cash to use for debt repayments and personal expenditures, the newspaper said. The multimillionaire, one of Vietnam's 20 richest people, according to stock reports, is a major shareholder in several commercial banks. He is also deputy chairman of the Vietnam Professional Football Joint Stock Co, which runs the V-League, and is chairman of the Hanoi Football Club. Besides banking and football, Kien also put money into many other areas, such as tourism and the garment industry. "Kien's arrest will affect not only the banking system and the stock market but also other economic sectors," Trung said.