The KOSPI, the benchmark index of the Korea Exchange, rose 90.59 points, or 1.4 percent, to 6,670.07 in early trade, while the KOSDAQ, the secondary board for smaller and technology-heavy companies, gained 2.3 percent to 808.31.
Breadth was overwhelmingly positive, with 608 stocks advancing against 207 decliners.
Foreign investors bought a net 112.1 billion won ($82.6 million), while institutions purchased a net 206.7 billion won. Individual investors sold a net 367.0 billion won.
The upside came from Washington. Federal Reserve Governor Christopher Waller said he would be inclined to support holding rates steady if incoming inflation data brought no surprises, pushing down expectations for a rate increase at the Fed's Sept. 15-16 meeting. The probability of a September hike implied by futures fell to 50.4 percent from 63.2 percent a day earlier.
Wall Street rallied on the shift. The Dow Jones Industrial Average closed 624.16 points, or 1.18 percent, higher, while the Nasdaq Composite gained 366.23 points, or 1.4 percent.
Samsung Electronics rose 1.7 percent to 254,250 won. SK hynix, the leading supplier of high-bandwidth memory for the artificial intelligence server market, gained 2.4 percent to 1,634,000 won. SK Square, SK hynix's largest shareholder, added 1.1 percent to 992,000 won.
Oil-sensitive trades also stood out. Refiners climbed as a war premium remained embedded in crude prices amid renewed U.S.-Iran hostilities. S-Oil surged 9.3 percent and GS Holdings gained 5.5 percent. Brent crude has traded around $95 a barrel this week.
Airlines were the strongest sector on the main board, gaining 5.2 percent. Hanjin KAL, the holding company of Korean Air, jumped 7.8 percent.
Among major decliners, Samsung C&T, the group's construction and trading arm, fell 4.6 percent to 355,000 won.
Hyundai Motor rose 1.5 percent to 389,250 won, while Hanwha Aerospace gained 1.3 percent to 1,061,000 won.
Elsewhere in Asia, Japan's Nikkei 225 was up 0.2 percent at 64,343.88. The won strengthened against the U.S. dollar, with Hana Bank quoting the currency at 1,356.70 won per dollar, up 1.80 won from the previous close.
AJP Takeaways:
º KOSPI rises 1.4% as Samsung Electronics and SK hynix rebound from two-session declines.
º Fed Governor Christopher Waller's remarks cut September rate-hike odds to roughly 50%.
º Foreign and institutional investors turn buyers; refiners and airlines lead broader gains.
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