Investors' concerns about Middle East tensions cause decline in Asia-Pacific markets, including a 1.4% drop in Japan's Nikkei.

• Traders in Asia were assessing data on consumer inflation out of South Korea.
• As Iran fired ballistic missiles at Israel, both oil prices and the CBOE Volatility Index (.VIX) increased.

The markets in Asia-Pacific began with a decline on Wednesday morning, mirroring the downturn on Wall Street at the start of the month, as major indexes plummeted amid escalating tensions in the Middle East.

The S&P/ASX 200 in Australia opened with a 0.3% decline, while Japan's stock market began the day with a 1.4% drop. In South Korea, the Kospi fell 1% at the open, and the small-cap Kosdaq was down 0.8%.

The HSI's last close of 21,133.68 was higher than Hong Kong's futures, which were at 20,768. Markets in Mainland China were closed Wednesday and will remain closed for the rest of the week due to the Golden Week holiday.

South Korea's consumer price index increased by 1.6% in September compared to the same month last year, according to data released Wednesday morning. This was lower than the 1.9% increase predicted by economists surveyed by Reuters.

In the U.S., the Dow Jones Industrial Average fell more than 173 points overnight, while the S&P 500 and Nasdaq Composite dropped 0.93% and 1.53%, respectively. Oil prices and the CBOE Volatility Index (.VIX) jumped as Iran fired ballistic missiles at Israel. The attack followed Israel's start of a ground operation into Lebanon as tensions escalated with Iran-backed militant group Hezbollah.

Benjamin Netanyahu, the Israeli Prime Minister, stated that Iran's missile attacks had failed and promised retaliation. He declared, "Iran made a grave mistake tonight — and it will pay the price," according to NBC News. He emphasized, "The regime in Iran does not comprehend our resolve to safeguard ourselves and our resolve to retaliate against our adversaries."

—CNBC's Brian Evans and Alex Harring contributed to this report.