The Hang Seng Index lost 120 points, or 0.5 percent, to open at 23,859 points on Wednesday.
Mainland stocks also opened lower, with the benchmark Shanghai Composite Index down 0.04 percent to open at 3,386 points.
The Shenzhen Component Index opened 0.09 percent lower at 10,142 points.
Concerns over escalating hostilities in the Middle East stayed front and centre in markets, sending oil prices higher.
Brent crude futures were up 0.33 percent to US$76.70 per barrel while US crude rose 0.45 percent to US$75.18 a barrel.
The spike in oil prices is a negative for the yen and euro at the margin as both Japan and the European Union are major importers of energy, while the United States is an exporter. (Agencies)
