The trading volume of South Korea's derivatives market expanded nearly 9 percent in the first half of the year on the back of a bullish stock market, the financial regulator said Friday.

The combined turnover of derivatives, such as stock options and futures, reached 20,047 trillion won ($18.4 trillion) in the January-June period, up 8.6 percent from a year earlier, according to the Financial Supervisory Service.

Exchange trading jumped 11.4 percent on-year to 13,267 trillion won, while the turnover of over-the-counter transactions climbed 3.6 percent.

The increase was attributed to the bull run of the local stock market that led to a surge in transactions of stock-related derivatives with their turnover jumping 19.5 percent on-year in the six-month period.

Trading by securities companies posted the highest 58 percent on-year growth, followed by banks with 32 percent and trust companies with 2.6 percent.

Market watchers expected the turnover of derivatives transactions to increase sharply in the latter half of the year, with the full-year tally marking a sharp turnover from a downtrend in recent years.

Last year, the turnover of the derivatives market came to 39,652 trillion won, down 11.2 percent from the previous year. (Yonhap)