Demand for the Hong Kong dollar hasn’t been this strong since Ant Group planned the world’s biggest IPO in the city almost five years ago. (Beijing later pulled the deal.) The resulting surge is prompting intervention.

The Hong Kong Monetary Authority has sold over a 100 billion in Hong Kong dollars in the foreign-exchange market this month.

Hong Kong's de-facto central bank stepped into the foreign exchange market on Tuesday as the currency hit the top end of its band for a fourth time this month, spurred by a broader selloff in the U.S.