Beijing has warned Slovakia and the Czech Republic that nobody should harbour any illusions about the "necessary measures" China will take to defend its sovereignty, ahead of a visit to both countries next week by Taiwan's foreign minister.
China, which claims democratically-ruled Taiwan as its own territory, is always angered by visits of senior Taiwanese officials to other countries, viewing it as covert support for the island's claims to be a state.
Taiwan Foreign Minister Joseph Wu will be visiting Slovakia and the Czech Republic next week, first attending a forum in Slovakia organised by a local think tank, and then going to Prague to meet the Czech parliament upper house speaker, Milos Vystrcil, and Prague Mayor Zdenek Hrib.
Chinese Foreign Ministry spokesman Wang Wenbin said they would be watching Mr Wu's "scuttling about" closely.
Asked if China will make steps against the Czechs and Slovaks, he said China "will take proper and necessary measures to firmly defend national sovereignty and territorial integrity. No one should have illusions about this".
Mr Wang did not elaborate.
China is already in a dispute with Lithuania after it agreed with Taiwan to open de facto embassies in each other's capitals.
Both China and Lithuania have recalled their envoys to the respective countries.
Taiwan has diplomatic ties with no European countries apart from the Vatican City.
Due to Chinese pressure, many countries are unwilling to host senior Taiwanese ministers, though Mr Wu visited Denmark in 2019 to speak at the Copenhagen Democracy Summit.
China has ramped up its military and diplomatic pressure against Taiwan to force it to accept Chinese sovereignty.
Taiwan says it is an independent country with a right to be treated as such internationally, and that it will defend itself from China if attacked.