The attack, which killed at least 12 people, was the deadliest on Ukraine’s capital in nearly a year. President Trump called on President Vladimir V. Putin to “STOP!” in a post on social media.

The attacks throw yet more doubt on already fraught efforts to push Russia and Ukraine to agree to a ceasefire.

A Russian drone has hit a bus carrying workers in the Ukrainian city of Marhanets, killing nine people in a wave of attacks that targeted civilian infrastructure in east, south and central Ukraine, officials said.