Turnover of South Korea's main and secondary bourses dropped sharply last month as investor sentiment was dampened by a recent Ponzi scheme that has rocked the local financial market, data showed Tuesday.

The average daily turnover of the main Kospi and tech-heavy Kosdaq markets stood at 18 trillion won ($13.8 billion) in May, down 31.7 percent from the previous month's 26.4 trillion won, according to the data from the Korea Stock Exchange.

The average daily transactions of the Kospi market slumped 27.5 percent on-month to 9.1 trillion won last month, while the Kosdaq saw its May daily turnover plunge 35.5 percent to 8.9 trillion won.

Experts noted that the sharp decline in turnover of the local stock market came as investors remained cautious due to a large-scale stock manipulation case involving SG Securities Korea Co., the local branch of Societe Generale Group of France, earlier this year.

About 1,000 investors are said to have suffered huge losses estimated to be between 800 billion won and 1 trillion won.

Meanwhile, the Kospi gained 3.02 percent to close at 2,577.12 points in May and the Kosdaq climbed 1.67 percent to 856.94 points. (Yonhap)