This photo, taken Thursday, shows the trading room of Hana Bank in Seoul as South Korean stocks soared nearly six percent on a chip rally and eased U.S. bond market concerns. Photo by Yonhap

Seoul shares soared nearly 6 percent Thursday as investors bet on stronger shareholder returns from chip giants Samsung Electronics and SK hynix, and eased U.S. bond market concerns. The Korean won fell against the U.S. dollar.

The benchmark Korea Composite Stock Price Index (KOSPI) rose 381.41 points, or 5.89 percent, to end at 6,852.58, after rising as high as 6,904.55.

The index plunged nearly 6 percent the previous session on a tech sell-off but recovered the losses after SK hynix announced a 40 trillion-won (US$28.7 billion) share buyback plan, while speculation grew over Samsung Electronics' shareholder return policy announcement later this month.

Program trading for the KOSPI-listed shares was suspended for five minutes at around 10 a.m., as the Korea Exchange (KRX) activated a buy-side sidecar, a measure triggered when the KOSPI 200 Futures Index rises 5 percent or more for at least one minute.