Bangkok. Asian shares tumbled Wednesday, with South Korea’s benchmark plunging as much as 11%, while oil prices climbed further.

Worries over the widening war with Iran have battered global markets. Rising oil prices — and concerns about how much they could fuel inflation — are unsettling investors who fear prolonged energy spikes could slow the global economy and erode corporate profits.

South Korea’s Kospi led regional losses as energy security concerns outweighed optimism over gains by major technology companies such as Samsung Electronics and SK Hynix, which have benefited from expanding use of artificial intelligence.

By midday, the Kospi was down 9.6% at 5,235.72. Samsung shares fell more than 10%, while SK Hynix dropped 8%.

The Korea Exchange temporarily halted trading of the Kospi index, and a circuit breaker was triggered on the tech-heavy Kosdaq after it slid more than 8%.

South Korea’s market has been among the world’s best performers this year, driven by semiconductor stocks lifted by the global AI boom. But concerns are mounting over the outlook for the trade- and fuel-import-dependent economy as the Middle East conflict intensifies and Iran threatens to close the Strait of Hormuz, the narrow gateway to the Persian Gulf through which roughly a fifth of globally traded oil passes.

In Tokyo, the Nikkei 225 fell 3.9% to 54,090.11. Japan, like South Korea and Taiwan, relies heavily on oil and liquefied natural gas imports from the Middle East that are now stranded in the Persian Gulf.

Elsewhere in Asia, Hong Kong’s Hang Seng Index lost 2.8% to 25,037.92 and the Shanghai Composite Index dropped 1.3% to 4,069.09.

In Australia, the S&P/ASX 200 declined 2% to 8,896.50. Taiwan’s Taiex fell 3.4%, while shares in Jakarta slid 3.7%.

On Tuesday, the S&P 500 closed down 0.9% at 6,816.63 after falling as much as 2.5% earlier in the session. The Dow Jones Industrial Average lost 0.8% to 48,501.27, and the Nasdaq Composite fell 1% to 22,516.69.

In the bond market, Treasury yields jumped in morning trading amid inflation concerns. The yield on the 10-year Treasury briefly rose above 4.10% before easing to just below 4.06%. It stood at 4.05% late Monday and 3.97% on Friday.

Higher yields increase borrowing costs for US households and businesses, affecting everything from mortgages to bond issuance. They also put downward pressure on stock prices and other investments.

Some analysts say they do not believe the sell-off marks the start of a prolonged downturn and that markets could rebound if the conflict proves short-lived. Still, Tuesday’s volatility underscored deep uncertainty.

The most immediate impact has been at the pump. The average US gasoline price jumped 11 cents overnight. In Europe and parts of Asia, drivers lined up to fill their tanks.

In the US, regular gasoline averaged $3.11 per gallon, according to motor club AAA. Prices had already been rising as refiners switched to summer fuel blends before US strikes on Iran.

Although the United States is a net oil exporter and does not face supply shortages, domestic fuel prices are shaped by global market trends.

Higher inflation linked to the conflict could complicate policy for the Federal Reserve. The Fed cut interest rates several times last year and signaled further reductions in 2026. While lower rates can support growth and employment, they can also add to inflationary pressures.

US benchmark crude rose 1.2% to $75.46 per barrel. Brent crude, the international standard, gained 1.5% to $82.61 per barrel.

The US dollar was nearly unchanged at 157.55 Japanese yen, while the euro edged down to $1.1599 from $1.1600.