At least four people died overnight as Russian drone and missile strikes continued to pound Ukraine’s towns and cities, local officials said Saturday. Meanwhile, Moscow’s troops continued their grinding advance through the country’s east.

Recent social media videos show Ukrainian forces using drones similar to IEDs. The drones sit next to roads and then strike Russian military vehicles when they pass.

A Russian drone struck a multi-storey apartment building in the northeastern Ukrainian city of Sumy early on Thursday, killing nine people and injuring 13, including a child, President Volodymyr Zelenskiy said.