Officials say a Russian drone barrage has targeted the center of Kharkiv, injuring nine people and damaging a maternity hospital in Ukraine’s second-largest city.

Russian drones bore down on the Ukrainian capital Kyiv early on Thursday, with officials reporting fires in apartment and non-residential buildings a day after a record number of drones targeted the country.

With their dense mesh, the nets can tangle drone propellers. It’s a simple but effective countermeasure that reflects how low-tech means can blunt high-tech weapons in the war.