The mayor of Prague, Zdenek Hrib, has warned Western societies to be aware of the Chinese Communist Party’s influence across the globe.

Last month, the capital of the Czech Republic broke off its relationship with Beijing and agreed to sign a sister city deal with Taiwan’s capital, Taipei, which has been separately ruled since the Chinese civil war of the 1940s. China insists that it should unite with Taiwan, by use of force if needed.

The mayor accused Beijing for attempting to impose an “uni...