South Korean stocks closed at a record-high level on Thursday as investors' sentiment was boosted by overnight gains on Wall Street. The Korean won gained against the US dollar.

The benchmark Korea Composite Stock Price Index soared 17.72 points, or 0.74 percent, to close at a fresh record high of 2,409.49. Trade volume was low at 284 million shares worth 6.05 trillion won ($5.32 billion), with gainers slightly outnumbering losers 397 to 396.

The index reached an all-time intraday high of 2.422.26 points, but pared earlier gains due to sell-offs by individual and institutional investors.

Analysts said Seoul shares closed higher on the back of improved investor sentiment at Wall Street after US Federal Reserve Chair Janet Yellen voiced support for a gradual increase of key interest rates.

The market rally also came amid the improved outlook over corporate earnings for the second half of 2017.

"While (listed companies') second quarter earnings growth slowed, investors' sentiment is being boosted by the outlook that their earnings will improve over the second half," said Lee Chang-mok, a researcher at NH Investment & Securities Co.

Foreigners bought a net 369 billion won, while institutions sold a net 177 billion won. Retail investors offloaded a net 243 billion won.

Market behemoth Samsung Electronics shot up 1.36 percent to a fresh record high of 2,528,000 won, and its smaller local rival LG Electronics moved up 0.56 percent at 71,200 won.

No. 2 chipmaker SK hynix also advanced 2.47 percent to close at a record 70,600 won. During the session, it reached 71,900 won to set a new record.

Steelmakers were also among winners, with industry leader POSCO advancing 2.94 percent at 315,000 won and Korea Zinc increasing 1.75 percent at 466,000 won. No. 2 steelmaker Hyundai Steel moved up 1.63 percent at 62,400 won.

Foodstuff makers, on the other hand, closed lower. CJ Cheiljedang decreased 0.14 percent at 355,000 won and Orion shed 2.28 percent to 81,600 won.

The local currency closed at 1,136.30 won against the US dollar, up 8.80 won from the previous session's close. 

Bond prices, which move inversely to yields, closed higher. The yield on three-year Treasurys fell 1.7 basis points at 1.745, and the return on the benchmark five-year government bond lost 2.1 basis points to 1.937 percent. (Yonhap)