An overview of Saki Airbase after attack, in Novofedorivka

An overview of aircraft at Saki Airbase after an attack in Novofedorivka, Crimea, on Thursday.

KYIV/NEW YORK — Russia and Ukraine accused each other on Thursday of shelling Europe’s biggest nuclear power plant as the U.N. chief proposed a demilitarized zone at the site amid fears of a catastrophe.

Ukraine’s Energoatom agency said the Zaporizhzhia complex was struck five times on Thursday, including near where radioactive materials are stored. Russian-appointed officials said Ukraine shelled the plant twice, disrupting a shift changeover, Russia’s TASS news agency said.