No casualties were reported after the strike at Yahodyn, which hit the train's engine. All the passengers had been evacuated, Ukrainian authorities said.
Johnson and other European national security advisers, including the UK's Jonathan Powell, had passed along the same line on a different train on their way back from a conference in Kyiv.
Russia said it had struck "railway infrastructure" in western Ukraine, but Ukraine's state railway company Ukrzaliznytsia said that "quite possibly, the target of this drone could have been the diplomatic train".
