The overnight strikes with Iranian-made drones capped a day in which Russian forces unleashed a major barrage of missiles on critical sites around Ukraine.

Russia launched a new swarm of Iranian-made drones overnight, Ukraine’s Air Force said on Saturday, attacking critical infrastructure in several regions after unleashing a barrage of cruise missiles, antiaircraft missiles and drones on cities across Ukraine.

The overnight drone attack caused serious damage to Ukraine’s already battered power grid, which Russia has repeatedly targeted in what military analysts say is a strategy of plunging the country into cold and darkness to lower morale.

The strikes, the first heavy aerial assault in weeks, occurred as fighting on the ground has intensified, with Ukrainian officials saying that Russian forces are mounting a major new push to seize control of the entire Donbas region of eastern Ukraine.

Air-defense systems destroyed 20 of the Shahed 136 drones between 6 p.m. and midnight, the Ukrainian Air Force said in a statement early Saturday. But three energy facilities in the Dnipro region of southeastern Ukraine were hit, including one in Kryvyi Rih for the second time in a day.

“They targeted our critical infrastructure,” Serhii Lysak, the head of the regional military administration,

The State of the War

• Zelensky’s U.K. Trip: President Volodymyr Zelensky of Ukraine pleaded with Britain to supply his country with fighter jets, making his dramatic appeal during a surprise visit to London.
• A New Offensive: As the war intensifies in Eastern Ukraine, doctors struggle to handle an influx of injuries and soldiers fret over the prospect of new waves of conscripts arriving from Russia.
• A Bloody Price: In its new push in the east, Russia is relying on masses of troops to overrun Ukrainian positions. The strategy has come at a cost of hundreds of dead and wounded soldiers each day.
• Leadership Shake-Up: Mr. Zelensky’s political party will replace Ukraine’s defense minister, Oleksii Reznikov. The expected move comes amid a widening corruption scandal, although Mr. Reznikov was not implicated in wrongdoing.