The Hang Seng Index lost 0.94 percent to open at 23,207 points on Monday.
On the mainland, the Shanghai Composite Index opened 0.24 percent lower at 3,343.34 points, while the Shenzhen Component Index opened 0.45 percent lower at 10,559.66 points.
On Monday, official data showed the mainland's manufacturing activity expanding at its fastest pace in a year in March.