Russia's War in Ukraine: Live Updates - The New York Times

Artillery fire resumes from the Zaporizhzhia nuclear plant, as more civilians flee the area.

The West has urged a demilitarized zone around the Zaporizhzhia nuclear plant.

ZAPORIZHZHIA, Ukraine — Artillery fire resumed on Sunday from the direction of a nuclear power plant in southern Ukraine, with shells streaking into a town from which the Ukrainian army has been unable to return fire, for fear of causing a meltdown or releasing radiation at the plant.

Hours before the barrages, there were reports that conditions were unraveling in and near the Zaporizhzhia Nuclear Power Plant.

The plant is the first active nuclear power plant in a combat zone.

The United States and European Union have called for the formation of a demilitarized zone, as the fighting in and around the plant and its active reactors and stored nuclear waste has sparked particular worry.

Ukraine’s president, Volodymyr Zelensky, said in his nightly address on Saturday that Russia had resorted to “nuclear blackmail” at the plant, reiterating a Ukrainian analysis that Moscow was using it to slow a Ukrainian counteroffensive toward the Russian-occupied city of Kherson, where Russian conventional military defenses appear increasingly wobbly.

Russia says it’s Ukrainian forces who are shelling the plant.

After pressurized water reactors failed at the Fukushima nuclear plant in Japan in 2011, Ukraine upgraded the Zaporizhzhia site to enable a shutdown even after the loss of cooling water from outside the containment structures, Dmytro Gortenko, a former plant engineer, said in an interview.

Ukraine’s military intelligence agency said that on Saturday, Russian artillery fire hit a pump, damaged a fire station and sparked fires near the plant that could not be immediately extinguished because of the damage to the fire station.

Overnight into Sunday morning, Russian howitzers fired on the Ukrainian town of Nikopol, which lies across a reservoir from the power plant, Yevheny Yetushenko, the Ukrainian military governor of the town, said in a post on Telegram.

The Ukrainian military has said it has few options for firing back.

The European Union and the United States in recent days have called for a demilitarized zone to be established immediately around the Zaporizhzhia Nuclear Power Plant in southern Ukraine, as shelling at the plant raises the risk of a nuclear accident.

While such plants are designed to withstand a range of risk — from a plane crashing into the facility to natural disasters — no operating nuclear power plant has ever been in the middle of active fighting, and this one was not designed with the threat of cruise missiles in mind.

If a fire were to break out at the power transformers and the electric network were taken offline, that could cause a breakdown of the plant’s cooling system and lead to a catastrophic meltdown, said Edwin Lyman, a nuclear power expert at the Union of Concerned Scientists, a private group in Cambridge, Mass.