South Korean stocks opened marginally lower Thursday before soon turning to positive terrain, as investors kept a close eye on the planned vote by US Congress on lifting the federal debt ceiling.

After starting lower at the opening bell, the benchmark Korea Composite Stock Price Index added 1.56 points, or 0.06 percent, to 2,578.68 in the first 15 minutes of trading.

US stocks closed lower Wednesday as the House of Representatives was set to vote on a bill to raise the $31.4 trillion debt limit to avoid a default. The bill needs to get congressional approval before the June 5 deadline.

Data indicating a strong US jobs market in April stoked jitters over the possibility of the Federal Reserve hiking the interest rate at the next policy meeting set for June 13-14.

Large-cap tech stocks traded mixed on the Kospi, with Samsung Electronics losing 0.14 percent and battery maker Samsung SDI rising 0.3 percent.

Chip giant SK hynix fell almost 1.5 percent, and top automaker Hyundai Motor was down about 1 percent.

Leading energy company SK Innovation advanced 2.4 percent.

The local currency was trading at 1,319.70 won against the US dollar at around 9:15 a.m., up 7.5 won from Wednesday's close. (Yonhap)