Air assaults on Saturday killed at least four people. Kharkiv’s mayor described an overnight strike as “the most powerful attack” since the beginning of the war.

The Ukrainian city of Sumy is near the Russian border, but far from the current front. Russia has amassed tens of thousands of troops in the region and occupied several villages. Could a greater incursion be coming?

Russian forces are advancing in the northern Ukrainian region of Sumy, bringing the regional capital within range of their drones and artillery, according to Ukrainian officials and analysts.