South Korean stocks opened markedly higher on Thursday on rising hopes for a possible peace deal between the United States and Iran, and an end to labor unrest at Samsung Electronics, triggering a buy-side sidecar.

After starting 3.85 percent higher, the benchmark Korea Composite Stock Price Index (KOSPI) rose 277.42 points, or 5.27 percent, to 7,388.52 as of 9:30 a.m, reports Yonhap news agency.

As stocks extended gains, a buy-side order in the KOSPI futures was suspended for five minutes at around 9:23 a.m., according to the Korea Exchange.

Overnight, U.S. stocks advanced as crude oil prices declined after reports that U.S. President Donald Trump said Washington was in the "final stages" of talks with Iran.

The S&P 500 rose 1.08 percent, while the Dow Jones Industrial Average gained 1.31 percent. The tech-heavy Nasdaq composite added 1.55 percent.

Investor sentiment improved after Samsung Electronics reached a tentative agreement with its labor union, easing concerns over a major strike that had been scheduled to begin Thursday at the world's largest memory chipmaker.

Tech shares gained as U.S. chip giant Nvidia forecast second-quarter revenue above Wall Street expectations and announced an $80 billion share repurchase program.

Major chipmakers opened sharply higher, tracking overnight gains on Wall Street.

Market top-cap Samsung Electronics surged 6.07 percent, and its chipmaking rival SK hynix advanced 4.53 percent.

Shares of Samsung affiliates also traded strongly. Samsung Electro-Mechanics skyrocketed 8.77 percent, and Samsung Life jumped 11.54 percent.

Auto shares moved higher. Auto giant Hyundai Motor increased 7.77 percent, and its sister Kia climbed 8.77 percent. Its auto parts affiliate Hyundai Mobis vaulted 18.32 percent.

The Korean won was trading at 1,499.0 won against the U.S. dollar at 9:15 a.m., up 6.9 won from the previous session.