For weeks, Russia and Ukraine have blamed each other for firing artillery at the Zaporizhzhia nuclear plant in southern Ukraine, the largest power station in Europe, in a series of attacks that imperil not just the region but also the whole world.

As the power plant inches toward a possible crisis, both sides have acknowledged the risks of a potential nuclear accident and continued fraught negotiations this weekend to let United Nations inspectors visit the site — and yet the bombardment continued.

Increased barrages near the plant struck towns, ammunition dumps and a Russian military base in intense fighting Sunday morning, Ukrainian officials said, raising questions about whether the area would ever be secure enough to allow inspectors anywhere near the plant.