Foreign Ministry spokesperson Zhao Lijian said Lithuania would “reap what it sows,” but gave no details.
The office, which opened Thursday, bears the name Taiwan rather than “Chinese Taipei,” which is used by the International Olympic Committee and many foreign nations to avoid offending China, which claims the self-governing island democracy as its own territory.
It wasn't clear what actions China plans to take in response to the opening of the office. Beijing has already recalled its ambassador from Vilnius and expelled the Lithuanian ambassador.
Lithuania plans to open a representative office in Taipei by the end of the year and has withdrawn from the “17 plus one” arrangement launched by China to bind it closer to countries in Eastern Europe.
China's threat underscores its extreme sensitivity to any challenge to what it considers its “core interests," as it presses ahead with its increasingly assertive foreign policy.