Add Yahoo as a preferred source to see more of our stories on Google. Ukraine has imposed sanctions against Belarus President Aliaksandr Lukashenka, Volodymyr Zelenskyy announced on Wednesday, saying Kyiv will "significantly intensify countermeasures against all forms of his assistance in the killing of Ukrainians".

At first, they might not seem like much of a threat: weather balloons, filled with helium or hydrogen, carrying bundles of cigarettes from Belarus.