06:43 AM EDT, 03/23/2026 (MT Newswires) -- Asian stock markets retreated Monday after US President Donald Trump issued a 48-hour ultimatum to Iran to open the oil-chokepoint Strait of Hormuz, or face strikes on its power plants.

Tehran announced that it would reply in-kind, by bombarding power and water infrastructure across the Persian Gulf region.

Hong Kong, Shanghai and Tokyo exchanges finished in the red, as did other regional trading floors, led by a 6.5% slip on Seoul's KOSPI index.

In Japan, the Nikkei 225 opened lower and drifted, finishing off 3.5% as traders weighed Middle East war drums, and regional oil supplies.

The benchmark Nikkei 225 fell 1,857.04 to 51,515.49, as losing issues outnumbered gainers 215 to nine.

Leading the upside was drugmaker Daiichi Sankyo, up 2%, while Mitsubishi Materials declined 9.3%.

In Hong Kong, the Hang Seng Index opened lower and declined to the close, concluding down 3.5% on the Middle East war outlook.

The broad gauge Hang Seng fell 894.85 to 24,382.47, as losing issues outnumbered gainers 88 to two. The Hang Seng TECH Index lost 3.3% on the day, while the Mainland Properties Index fell 3.9%.

Leading the upside was Geely Automobile, gaining 2.5%, while Laupu Gold declined 8.6%.

On the mainland, the Shanghai Composite fell 3.6% to 33,813.28.

On the other regional exchanges, the Taiwan TWSE declined 2.5%; the Australian ASX 200 declined 0.7%; the Singapore Straits Times Index fell 2.2%, and the Thai Set declined 2.5%. In late trading in Mumbai, the Sensex was down 2.5%

The MSCI All Country Asia Pacific Index fell 3.7% on the day.