A Russian plot to kill a Ukrainian-American citizen in Warsaw was thwarted by Poland before it could be carried out, the Polish prime minister said Thursday, marking the first time in decades that a Western leader has publicly accused Moscow of plotting to kill a U.S. citizen. Western officials have previously warned that Russia has stepped up a campaign of targeted killings since President Vladimir Putin launched the 2022 invasion of Ukraine, saying they have disrupted several plots across Europe. But Polish Prime Minister Donald Tusk said this incident was unprecedented.