The Tokyo stock exchange's Nikkei 225 index was down 0.7 percent when investors took a break for lunch, while the broader Topix index stood at minus 0.6 percent.
In Hong Kong, the Hang Seng index was down 1.5 percent at the same time. Shanghai and Shenzhen's composite index pointed to minus 0.6 and minus 0.9 percent, respectively.
South Korea's Kospi index stood at minus 0.3 percent.
Fears that the clashes between Israel and Iran will expand have contributed to pushing up the oil price. Iran is partly an oil exporter, but the country is also located next to the Strait of Hormuz, where a large part of the world's crude oil passes through.
The US central bank, the Federal Reserve (Fed), announced on Wednesday that the key interest rate remains unchanged, a decision that was expected. Fed chief Jerome Powell warned after the interest rate announcement that "we are starting to see some effects" on inflation from President Donald Trump's tariffs.
