Day trading of shares in Korea doubled in 2015 from a year earlier as overall stock transactions rose and mobile gadgets boosted convenience for investors, the bourse operator said Monday.

The Korea Exchange said day trading came to 119.4 billion shares worth 658 trillion won in 2015 on the benchmark KOSPI and the tech-laden KOSDAQ markets.

Last year's trading volume was up 100 percent from 59.7 billion shares in 2014, with the turnover rising 98.7 percent from 331 trillion won, according to the KRX.

Day trading refers to the act of buying and selling shares several times during the same day to seek profits from price movements.

In terms of volume, day trading accounted for 45.43 percent in 2015, up 6.9 percentage point from a year earlier, the highest level since 2012.

"The increase is attributable to the overall growth in stock trading last year, and the widespread use of smartphones and trading applications," the KRX said in a release.

In 2015, a total of 262.8 billion shares were traded on the KOSPI and KOSDAQ markets, up from the previous year's 155 billion.

The proportion of trading through mobile devices also hit an all-time high of 27.33 percent in 2015, up from the previous year's 21.5 percent, according to KRX data. 

By market, day trading accounted for 43.73 percent on the KOSPI and 46.71 percent on the KOSDAQ markets, according to the KRX, noting that retail investors carried out day trading, accounting for 97.02 percent of the total volume. (Yonhap)