Overseas markets opened the new week under renewed pressure Monday, Sept. 28, as rising crude oil prices, elevated U.S. Treasury yields and continuing uncertainty surrounding the U.S.-Iran conflict weighed on investor sentiment across much of Asia.
September 28, 2026 (STL.News) Overseas Markets – The trading session, which began Sunday evening for U.S. investors, produced significant losses in South Korea and mainland China, while Japanese stocks also retreated. Hong Kong and Australia posted modest gains, reflecting an uneven response to the latest mix of geopolitical and interest-rate risks.
Oil was once again at the center of the global market story. Brent crude moved above $107 a barrel during Asian trading as investors reassessed prospects for an agreement involving Iran and the strategically important Strait of Hormuz.
Meanwhile, long-term U.S. Treasury yields stayed near multiyear highs, increasing pressure on technology and other growth-oriented stocks.
Overseas Markets – Overseas Market Snapshot
Japan’s Nikkei 225 fell 486.58 points, or 0.73%, to 65,877.62. The broader TOPIX declined 16.59 points, or 0.40%, to 4,112.00.
South Korea suffered one of the session’s largest declines. The KOSPI dropped 191.18 points, or 2.70%, to 6,889.74, falling back below the 7,000 level after markets reopened following the Chuseok holiday.
Mainland Chinese equities also fell sharply. The Shanghai Composite fell 64.75 points, or 1.67%, to 3,823.62.
Hong Kong moved against the broader regional trend. Later Asian market data showed the Hang Seng at 24,642.51, up 132.42 points, or 0.54%.
Australia’s S&P/ASX 200 gained 14.68 points, or 0.17%, to 8,679.69.
The differences between markets underscored that Monday’s trading was not a uniform global selloff. Nevertheless, declines in China, South Korea and Japan left the broader Asian picture tilted toward risk reduction.
Overseas Markets – Oil Returns to Center of Market Concerns
Crude oil was arguably the most important cross-market influence.
Brent crude climbed sharply after President Donald Trump rejected an Iranian proposal intended to help end the conflict and reopen the Strait of Hormuz, although further negotiations remained possible.
During Asian trading, Brent reached approximately $107.16 a barrel, up about 2.7% at one point. U.S. crude was around $94 a barrel.
The Strait of Hormuz remains critical because it is one of the world’s most important energy transit routes. Prolonged restrictions or uncertainty surrounding shipments through the waterway can affect global petroleum supplies and transportation costs.
For equity investors, the concern extends beyond energy companies.
Sustained oil prices above $100 could increase transportation, manufacturing, and consumer costs, complicating the global inflation outlook. Higher energy-driven inflation could, in turn, force central banks to maintain tighter monetary policy than investors previously anticipated.
That connection between oil, inflation and interest rates has become one of the dominant themes influencing global markets.
Overseas Markets – Treasury Yields Add Pressure
The bond market added another source of pressure.
The yield on the 30-year U.S. Treasury was around 5.52% during the Asian session, remaining near levels not seen in more than two decades.
Long-term yields have climbed as investors reassess inflation and monetary-policy expectations.
That creates a difficult environment for stocks, particularly companies whose valuations depend heavily on earnings expectations many years into the future.
Higher Treasury yields also make government bonds more attractive relative to equities. Investors can obtain considerably higher yields from relatively low-risk government securities than they could during the ultra-low-rate environment of previous years.
The effect can be particularly significant for technology shares.
When yields rise, the present value investors assign to future corporate earnings generally falls. That valuation pressure contributed to weakness in several technology-heavy Asian markets Monday.
U.S. stock-index futures also weakened during portions of the Asian session, with Nasdaq futures showing greater pressure than the broader S&P 500 futures.
Overseas Markets – South Korea Hit by Technology Selling
South Korea provided perhaps the clearest example of the pressure facing technology stocks.
The KOSPI closed 2.70% lower at 6,889.74, ending a four-session winning streak.
The index was closed Thursday and Friday for the Chuseok holiday, so Korean investors returned to several days of accumulated developments in global bonds, oil and geopolitics.
Large technology stocks were among the biggest sources of weakness.
Investors took profits in major semiconductor companies while foreign and institutional investors were heavy sellers. Samsung Electronics and SK Hynix were among the large technology names experiencing substantial pressure.
The selloff accelerated throughout the session. The KOSPI opened only about 0.33% lower before losses expanded dramatically.
By the close, the index had lost more than 190 points.
That progression matters because it suggests the decline was not simply an opening adjustment after the holiday. Selling intensified as the trading day continued.
Higher U.S. bond yields, profit-taking in technology shares and uncertainty surrounding the Middle East all contributed to the deterioration in sentiment.
Overseas Markets – China Extends Its Decline
Chinese equities faced a mix of pressures.
The Shanghai Composite finished 1.67% lower at 3,823.62, while losses in some technology and semiconductor shares were considerably larger.
Economic concerns contributed to the weakness.
Recent Chinese industrial-profit data showed continued challenges from softer domestic demand, even as parts of the technology sector remained comparatively strong.
Investors were also assessing additional U.S.-China technology tensions.
Those concerns arrived at a difficult time for Chinese equities, which have already been navigating questions about domestic growth, consumer demand and the country’s property sector.
The result was another substantial decline in mainland shares Monday.
Hong Kong performed considerably better, however, with the Hang Seng gaining approximately 0.5%.
The divergence between Hong Kong and mainland China is another reason Monday’s trading should be characterized as mixed but generally weaker, rather than as a universal Asian selloff.
Overseas Markets – Japan Retreats After Recent Strength
Japanese stocks also moved lower.
The Nikkei 225 closed at 65,877.62, down 0.73%, while the broader TOPIX declined 0.40%.
Japan has been one of the stronger major equity markets, supported partly by technology and artificial-intelligence enthusiasm. But higher global yields and renewed energy concerns gave investors reasons to take profits.
Japan also depends heavily on imported energy, making large increases in crude prices particularly relevant to the country’s economic outlook.
Higher oil prices can raise import costs and squeeze corporate margins while also putting extra pressure on household expenses.
Those factors helped limit enthusiasm for Japanese equities Monday.
Overseas Markets – Australia Bucks the Regional Decline
Australian stocks proved more resilient.
The S&P/ASX 200 gained approximately 0.17% to 8,679.69, avoiding the losses seen in Japan, South Korea and China.
Australia’s market composition differs significantly from technology-heavy Asian benchmarks. Its substantial exposure to mining, resources and financial companies can sometimes provide insulation when semiconductor and technology stocks are under pressure.
Still, Australia’s modest advance did little to shift the region’s generally cautious tone.
Overseas Markets – India Comes Under Heavy Pressure
The risk-off environment subsequently spread to India.
Indian stocks fell sharply during Monday trading as higher crude prices raised concerns for an economy that depends heavily on imported energy.
The Sensex fell more than 1,000 points during the session, reaching approximately six-month lows, while the Nifty 50 dropped below 22,900.
Rising crude is especially important for India because higher petroleum prices can increase the country’s import bill, pressure the rupee, and complicate inflation management.
Indian equities were also contending with continued foreign investor selling.
The decline demonstrated how an oil shock originating in the Middle East can have substantially different consequences depending on a country’s dependence on imported energy.
Overseas Markets – Iran and Hormuz Remain Critical Variables
Markets are likely to continue reacting quickly to developments involving the United States, Iran and the Strait of Hormuz.
Trump rejected Iran’s latest proposal, which included provisions aimed at reopening the waterway and ending fighting.
However, the diplomatic channel has not necessarily closed.
Iranian officials have continued to discuss diplomacy publicly, while Trump has indicated additional negotiations could occur.
That distinction matters for markets.
A definitive collapse in negotiations accompanied by further disruption to energy shipments could push crude prices higher.
Conversely, credible progress toward reopening the Strait of Hormuz could remove part of the geopolitical risk premium currently embedded in oil.
That makes geopolitical headlines unusually important to short-term movements in equities, bonds, currencies and commodities.
Overseas Markets – What U.S. Investors Should Watch Next
For U.S. investors preparing for the new trading week, the overseas session provides several important signals.
The first is oil.
Brent trading around $105 to $107 represents a materially different economic environment than oil below $100. Continued increases would intensify questions about inflation, corporate margins, and consumer spending.
The second is Treasury yields.
A 30-year yield around 5.5% represents substantial competition for equities and creates particular valuation pressure for technology and other high-growth stocks.
The third is the U.S. dollar.
Higher U.S. interest rates have helped support the dollar, which can create additional challenges for multinational companies and emerging markets.
Finally, investors should watch the interaction between technology stocks and bond yields.
South Korea’s Monday session reminded investors how quickly highly valued technology shares can come under pressure when investors simultaneously confront profit-taking, rising yields and geopolitical uncertainty.
Overseas Markets Send a Cautious Signal
The first major overseas trading session of the week did not produce a universal flight from equities.
Hong Kong and Australia finished higher.
But beneath those gains was a more cautious global picture.
South Korea dropped 2.70%. Mainland China lost 1.67%. Japan declined 0.73%. Indian equities subsequently suffered significant losses.
Meanwhile, Brent crude returned above $107 during the session, and long-term Treasury yields stayed near levels rarely seen over the past two decades.
Those developments create a challenging combination for global investors.
Higher oil threatens renewed inflation. Higher inflation increases pressure on central banks. Higher interest rates push bond yields upward, and higher bond yields make expensive equities harder to justify.
That chain of events is likely to remain central to markets as investors enter the final days of September.
For now, the overseas message heading toward the next U.S. session is one of caution rather than panic.
The decisive variables remain oil, Treasury yields and diplomacy surrounding Iran and the Strait of Hormuz. A meaningful change in any one of those could quickly alter the direction of global markets.
Until then, investors face an environment in which geopolitical risk, energy inflation, and historically elevated borrowing costs are once again competing with optimism around technology and artificial intelligence for control of the market narrative.
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