KYIV, Ukraine — Russia hit crucial electricity transmission facilities linked to nuclear power plants during its latest assault on Ukraine’s power grid on Thursday, the International Atomic Energy Agency reported. It was the third such attack in roughly as many months, heightening concerns among experts about the potential for a nuclear disaster.

Ukrainian officials say Russia has conducted a “massive” attack against Ukraine’s energy infrastructure, firing nearly 200 missiles and drones and leaving more than a million households without power

Energy workers are scrambling to fix damage to the Ukrainian power grid to keep people from freezing to death amid a massive attack by the Russian military. Vladimir Putin calls the attack retaliatory for Ukraine’s use of U.