Hong Kong stocks slumped 768.86 points or 4.08 percent to close Thursday's morning session at 18,055.31 points.
The benchmark Hang Seng Index hit half-day low of 18,019.44 after opening down 527.37 points, or 2.80 percent, at 18,296.80.
Turnover totaled 38.77 billion HK dollars so far.
Weakness was broad-based with all 46 blue chips but one went up.
Heavyweight HSBC sank 3.26 percent to 60.85 HK dollars, and China Mobile lost 2.44 percent at 77.85 HK dollars.
Bucking the trend, Fashion retailer Esprit added 0.67 percent to 9.02 HK dollars. (1 U.S. dollar equals 7.795 HK dollars)
Source: Xinhua