LONDON — A sell-off in global markets accelerated on Friday as tensions between the United States and North Korea escalated, driving investors toward havens.

Asian stock markets closed lower and European indexes opened sharply down on fears that the verbal back-and-forth between Washington and Pyongyang had raised the risk of actual conflict.

Hong Kong’s benchmark Hang Seng Index fell 2 percent, and South Korea’s main share index also dropped. Stock markets in Britain, France and Germany were all lower by noon in London.

Investors moved their money into what they apparently deemed safer assets. The Japanese yen and Swiss franc were both stronger, and the price of gold rose for the third consecutive day. The yields on British and European bonds, which move inversely to the price, fell.