At least three Ukrainian civilians were killed and 23 others were wounded by Russian shelling in 24 hours, including an attack not far from a Russian-occupied nuclear power plant, the office of Ukraine's president reported Tuesday.

The Russians fired over 120 rockets from Grad multiple rocket launchers at the southern town of Nikopol, which is across the Dnieper River from the Zaporizhzhia Nuclear Power Plant, Dnipropetrovsk Gov. Valentyn Reznichenko said. Several apartment buildings and industrial facilities were damaged, he said.

Ukraine and Russia accused each other in recent days of shelling the nuclear plant, which is the largest one in Europe, and increasing the risks of a nuclear accident.

In his nightly video address, Ukrainian President Volodymyr Zelenskyy invoked the 1986 disaster at the Chernobyl nuclear plant in Ukraine, which at the time was a Soviet republic. He called for new sanctions against Russia “for creating the threat” of another nuclear disaster.

“We are actively informing the world about Russian nuclear blackmail - about the shelling and mining of the Zaporizhzhia NPP facilities," Zelenskyy said. "Russia will not pay attention to words and concerns...The Chernobyl disaster is an explosion in one reactor; the Zaporizhzhia NPP is six power units.”

The Kremlin claimed Monday that Ukraine's military was attacking the plant and urged Western powers to force Kyiv to stop the activity.

A Russian-installed official in the partially occupied Zaporizhzhia region said an air defense system at the plant would be reinforced in the aftermath of last week's shelling. Evgeny Balitsky, the head of the Kremlin-backed administration, told Russian state TV Tuesday that power lines and damaged blocks of the plant were restored.

“The plant is operating normally, but, of course, with an increased degree of security,” Balitsky said.

A Ukrainian counteroffensive and Russian defensive actions in occupied areas has increasingly drawn firepower to southern Ukraine.

After failing to capture Ukraine's capital, Kyiv, early in the war, the Russian military focused its strength on trying to seize all of the country's eastern Donbas region. Pro-Moscow separatists have fought Russian forces in the region for eight years and control some territory as self-proclaimed republics.

The British Defense Ministry said Tuesday that Russian forces had made the most progress in the past month in moving toward the town of Bakhmut - an advance limited to about 10 kilometers (6.2 miles).

“In other Donbas sectors where Russia was attempting to break through, its forces have not gained more than 3 km during this 30-day period; almost certainly significantly less than planned,” the U.K. ministry said.

However, the ministry cautioned that despite the attention required in southern Ukraine, Russia had maintained attacks on Ukrainian positions in the east.

The governor of eastern Ukraine's Donetsk province, Pavlo Kyrylenko, said the Russians were trying to press their offensive in several areas. Kharkiv, the country's second-largest city, came under the Russian shelling four times over the past 24 hours, and some city infrastructure was damaged.