NIKOPOL, Ukraine — Russian shelling across the river from Ukraine’s main nuclear power plant wounded four people Monday, an official said, hours after the latest international pleas to spare the area from attacks to prevent a catastrophe.

Meanwhile, Russia blamed Ukrainian spy agencies for the car bombing on the outskirts of Moscow over the weekend that killed the daughter of a far-right Russian political thinker and ardent supporter of the invasion of Ukraine.

On the battleground, the city of Nikopol, about 10 kilometers (six miles) downstream from the Zaporizhzhya nuclear plant, came under fire three times overnight from rockets and mortar shells. Houses, a kindergarten, a bus station and stores were hit, authorities said.

Mayor Oleksandr Saiuk said four people were wounded, and two of them were hospitalized.

The reports of sustained shelling around Europe’s biggest nuclear plant further highlighted the dangers of a war that will hit the half-year mark on Wednesday.

After U.N. Secretary-General Antonio Guterres urged caution during a visit to Ukraine last week, U.S. President Joe Biden further discussed the issue with the leaders of France, Germany and Britain on Sunday.

The four leaders stressed the need to avoid military operations in the region to prevent a nuclear disaster and called for the U.N.’s atomic energy agency to be allowed to visit the plant as soon as possible.

On Saturday night, a car bombing killed 29-year-old TV commentator Darya Dugina, whose father, political theorist Alexander Dugin, is often referred to as “Putin’s brain.”

On Monday, Russia’s Federal Security Service, the main successor to the KGB, said the killing was “prepared and perpetrated by the Ukrainian special services.” It charged that the bombing was carried out by a Ukrainian citizen who left Russia for Estonia afterward.

The FSB said that the suspect, Natalya Vovk, rented an apartment in the building where Dugina lived and shadowed her. Vovk and her daughter were at a nationalist festival that Dugin and his daughter attended just before the killing, the FSB said.

Ukraine officials have denied any involvement.

On the Russian-occupied Crimean Peninsula, anxiety has spread following a spate of fires and explosions at Russian facilities over the past two weeks. The governor of Sevastopol, Mikhail Razvozhaev, ordered that signs showing the location of bomb shelters be placed in the city, which had long seemed untouchable.

Sevastopol, the Crimean port that is the home of Russia’s Black Sea Fleet, has seen a series of drone attacks. A drone exploded at the fleet’s headquarters on July 31, and another was shot down over it last week. Authorities said air-defense systems have shot down other drones as well.

Razvozhaev said on Telegram that the city is well-protected, but “it is better to know where the shelters are.”

Russian President Vladimir Putin didn’t directly mention the war during a speech marking National Flag Day on Monday but echoed some of the justifications cited for the invasion.

“We are firm in pursuing in the international arena only those policies that meet the fundamental interests of the motherland,” Putin said. He maintains that Russia sent troops into Ukraine to protect it against the encroaching West.