KYIV — Russia fired a wave of attack drones and missiles at Ukraine that killed at least four people, authorities said on Tuesday after the second night of heavy strikes across the war-battered nation.

The overnight barrage came a day after the Kremlin launched one of its largest-ever aerial attacks on Ukraine, which targeted energy facilities and killed several people.

Ukraine's air force said on Tuesday it downed half of the 10 missiles and 60 of the 81 Iranian-designed attack drones launched from several regions of Russia and the annexed Crimea peninsula.

"Unfortunately, despite the effective work of our air defense systems, four people were killed and 16 were wounded," President Volodymyr Zelenskyy said in a social media post.

He also said rescue work was ongoing at the impact sites and vowed a response to the attacks.

"Crimes against humanity cannot be committed with impunity," he said.

Agence France-Presse (AFP) journalists in the capital Kyiv heard air raid sirens echo over the city throughout the night, as well as an explosion, likely from air defense systems.

Repeat hotel attack

Local authorities said earlier on Tuesday that two people had been killed in the southeastern Zaporizhzhia region and two in the central city of Kryvyi Riv after a missile struck a hotel.

The hotel strike comes just days after a team working for the Reuters news agency were hit by a missile in their hotel in the eastern Ukrainian city of Kramatorsk, killing a safety adviser working with the agency.

The Russian attacks on Monday triggered widespread blackouts and spurred condemnation from Ukraine's allies in Europe and the United States.

Russia said the attack had targeted infrastructure linked to the Ukrainian military. North Atlantic Treaty Organization member Poland said its airspace was violated during the barrage, probably by a drone.

Since invading in February 2022, Russia has launched repeated large-scale drone and missile attacks on Ukraine, including punishing strikes on energy facilities.

In Kyiv, Ukraine's electricity grid operator said on Tuesday that emergency blackouts would be applied throughout the day to reduce pressure on the grid following the fresh attacks that damaged energy infrastructure nationwide.

"Ukraine's power system is currently recovering from nine massive Russian attacks, with a power deficit and emergency and scheduled repairs under way at power facilities," Ukrenergo said in a statement, urging Ukrainians to reduce their electricity consumption.

'Break through the border'

The bombardment comes as Ukrainian forces are pushing an offensive in Russia's border region of Kursk, a surprise operation that has seen Kyiv gain swathes of territory in three weeks.

Vyacheslav Gladkov, the governor of Russia's Belgorod region, which borders Kursk and Ukraine, said on Tuesday he was aware of reports the Ukrainian army had tried to cross the border.

"Information has emerged that the enemy is trying to break through the border of the Belgorod region," he said.

"According to the Russian defense ministry, the situation on the border remains difficult but under control," he said on social media.

Zelenskyy said on Monday night that Ukraine's surprise cross-border incursion into Kursk on August 6 was partially to "compensate" for Kyiv's inability to strike deeper into Russian territory.

He has been appealing to Ukraine's allies to allow his forces to use Western-supplied weapons to strike targets inside Russian territory as part of efforts to thwart more aerial bombardments.

Despite Ukraine's push inside Kursk, which Kyiv hoped would divert Russian forces from the frontline in the east of the war-battered country, Moscow has been making steady gains.

Zelenskyy said defending the logistics hub of Pokrovsk in the eastern Donetsk region was "difficult" and that Ukraine was strengthening its positions there as Russian forces advance.

Russia's Defense Ministry said on Tuesday its forces had captured the village of Orlivka, near Pokrovsk.

This week, AFP journalists saw civilians evacuating by train from Pokrovsk, once home to about 60,000 people, with panicked residents carrying their belongings in bags and pets with them.