The Russian authorities said on Saturday that a Ukrainian attack on the city of Belgorod had killed at least 22 people and injured nearly 110 others, in what would be the deadliest single assault against a Russian city since the start of the war nearly two years ago.
Russia’s Defense Ministry said in a statement that Ukraine had hit Belgorod — a regional center of around 330,000 residents about 25 miles north of the Ukrainian border — with two missiles and several rockets, adding that the strike was “indiscriminate.”
The ministry said that most of the rockets had been shot down, but that some debris had fallen on the city. The Ukrainian government has not officially commented on the Belgorod attack, and Russian claims could not be independently verified.
The attack seemed to be Ukraine’s response to a massive and deadly Russian air assault against its territory a day earlier, and another sign of Kyiv’s determination to bring the war to Moscow’s doorstep. In his overnight address on Friday, President Volodymyr Zelensky of Ukraine said that his country would continue to “work toward pushing the war back” to “where it came from — home to Russia.”
Saturday’s attack on Belgorod were quickly followed by what Ukrainian officials said were several Russian strikes against the Ukrainian city of Kharkiv, about 40 miles from Belgorod, in apparent cross-border retaliation.
The back-to-back assaults underscored how both Moscow and Kyiv remain willing to escalate a war that will most likely mark its two-year anniversary in February, despite Ukraine’s problems with securing Western funding, an increased sense of war fatigue in Russia and enormous casualties on both sides.
“There will always be an answer for all crimes,” Andriy Yermak, the head of the Ukrainian president’s office, wrote on social media on Saturday, while Russia’s Defense Ministry said that the attack against Belgorod would “not go unpunished.”
While the details of Saturday’s attack into Russia were not immediately clear, the death toll alone made it noteworthy. Many Russians have held onto a sense of relative normalcy despite the war, but the violence in Belgorod — which explosions have rocked repeatedly over the last two years — shattered that stability.
To many Ukrainians, the strikes bring home to Russia the kind of suffering that they have endured almost daily for nearly two years; to many pro-war Russians, they are evidence that Moscow must use even more aggressive tactics in Ukraine.
The Russian Emergency Situations Ministry posted a video of the aftermath of the bombardment that showed cars on fire, injured people being carried to shelter and broken glass on the city’s buildings. And Russian state television broadcast videos posted by residents of Belgorod that showed plumes of smoke over the city, shattered glass near residential buildings and people lying on pavements — in a striking echo of scenes that unfolded a day before in Ukrainian cities such as Kyiv, Lviv and Dnipro.
Vyacheslav Gladkov, the governor of the Belgorod region, said that three children were among those killed on Saturday and that a residential area in the city center had been hit.
An emergency U.N. Security Council meeting convened to discuss the attack, with Ukraine’s Western allies putting the blame squarely on the Kremlin, which started the war. “If Russia wants someone to blame for the deaths of Russians in this war, it should start with President Putin,” the British envoy, Thomas Phipps, told the Council.
On Friday, the same Council met to address Russia’s assault against Ukrainian cities, with the United States, France and Britain strongly condemning the attack.
Ukraine has said several times that it does not fear taking the war to Russian territory, and it has previously targeted the Belgorod region with cross-border strikes and even brief ground assaults by Kyiv-backed, anti-Kremlin Russian fighters.
So far, such attacks have resulted in at least 50 deaths inside Russia, according to the United Nations, as well as the evacuation of a few thousand civilians and minor clashes with the Russian military.
Saturday’s strike on Belgorod was in response to Russia’s air assault on Friday against Ukraine, said an official from Ukraine’s intelligence services, who spoke on the condition of anonymity to discuss the matter, adding that only military facilities had been targeted. The assault on Ukraine — one of the largest of the war — killed at least 39 people, wounded about 160 others and hit civilian and military infrastructure.
Ukrainian rescuers on Saturday were still pulling bodies from the rubble of a factory that was struck in central Kyiv, the capital, according to local authorities.
And on Saturday evening, the Ukrainian authorities said, Russia launched an assault on Kharkiv, Ukraine’s second largest city, in what appeared to be Russia’s own response to the Ukrainian attack.
Oleh Syniehubov, the head of the Kharkiv region military administration, said that Russian missiles fired from the Belgorod region targeted the eastern Ukrainian city and that at least 28 people had been injured in the attack. He added that the Russian military struck the city center six times and reported damage to residential buildings, shops and a medical facility.
Unverified videos and images shared on social media also showed that the Kharkiv Palace Hotel, one of the city’s most popular hotels and a frequent venue for foreign journalists, was hit. Photographs of the aftermath of the attack showed the facade of the building pierced by a huge hole the size of several stories.
Mr. Syniehubov also said that Russian shelling on a village in the Kharkiv region left three people dead. Their bodies were pulled from the rubble of their destroyed house.
The back-to-back air assaults on Friday and Saturday come as Ukrainian and Russian troops are bogged down on land in bloody and mostly inconclusive fighting. Moscow has made several advances all along the front in recent weeks, but military experts say its gains are incremental and unlikely to lead to a major breakthrough in the near future.
