Back in 1998, Hafez El-Assad's Syria was hosting Abdullah Öcalan, the leader of PKK, a Turkish Kurds' Organization that took both political and guerilla actions.
Turkey was quite angry about it and made explicit threats:
Turkey threatened to invade unless Syria curbed PKK activity in its territory. This approach worked. Syria kicked Ocalan out of the country, whereupon he was apprehended by Turkish officials, with American assistance, and sent to prison.
Other possible examples that come to mind and need further investigation are China's reaction to people meeting with the Dalai-lama, or USSR threats to countries meeting Trotsky or Tito.