The arrest of one of the highest-profile business tycoons in Vietnam triggered the country's largest stock market drop in four years, underlining vulnerability in the country's financial system, according to Bloomberg. 

Nguyen Duc Kien, who helped found Asia Commercial Bank, Vietnam’s fourth-biggest bank, was arrested on Monday, according to a central bank statement cited by the publication. Police are investigating violations at three companies managed by Kien, after he allegedly “conducted business illegally,” according to the statement.

Standard Chartered reportedly owns a 15 per cent stake in ACB.

Banking stocks fell nearly 5 per cent on the benchmark Ho Chi Minh City stock exchange yesterday after the news. Kien held a senior position managing Vietnam’s professional football league and his family was among the 30 wealthiest in the country last year.