In Hong Kong, the benchmark Hang Seng Index opened down 27 points, or 0.11 percent, at 24,380 before losses accelerated to 363 points, or 1.49 percent, at 24,044 at one stage in mid-morning trading.
The tech index was down nine points, or 0.2 percent, at 4,715 while the China enterprises index was six points, or 0.07 percent, lower at 8,312.
Over on the mainland, the Shanghai Composite Index opened down 13 points, or 0.34 percent, at 3,979.
The Shenzhen Component Index was 64 points, or 0.43 percent, lower at 14,889 while the ChiNext Index was down 15 points, or 0.4 percent, at 3,839.
The losses came after the United States began a fresh round of strikes against multiple targets in Iran, hours after President Donald Trump vowed new attacks if no peace deal is secured.
Iran announced the closure of the Strait of Hormuz in response.
Brent crude rose two percent to almost US$95 a barrel as trading resumed in Asia.
Strategists believe that Asian stocks that had rallied hardest during the past two months are likely to extend recent losses, as markets question whether the sky-high expectations for earnings growth that had driven the gains can be maintained.
“Given already stretched valuations, these extreme bullish expectations set a vulnerable backdrop for momentum in Korea, Taiwan and the Asia tech sector,” said Rupal Agarwal, Asia quant strategist at Bernstein in Singapore, in a note to clients.
Trimming positions in these stocks would be “most prudent,” she added, noting that “the re-escalation on the war front could further accelerate this unwind”.
In Tokyo, the Nikkei opened down 850 points, or 1.32 percent, down at 63,329 before trimming its losses to be 596 points, or 0.93 percent, lower at 63,583 at one stage before noon.
In Seoul, the Kospi plummeted 221 points, or 2.86 percent, to 7,509 at the opening before, like the Nikkei, trimming its losses to be 137 points, or 1.78 percent, lower at 7,593 at one stage before lunch. (Reuters/Xinhua)