Putin Vows to Keep Up Bombardment After a Russian City Is Hit

President Vladimir V. Putin of Russia vowed on Monday to continue missile strikes on Ukrainian cities, in retaliation for what he called a “terror” attack on the Russian city of Belgorod last week.

“They want to scare us, to create a certain uncertainty inside the country,” Mr. Putin said during a televised meeting with the veterans of the war in Ukraine. “From our side, we will build up the strikes.”

Mr. Putin’s rare public comments about an attack on the Russian territory comes as his armed forces in recent days have pummeled Ukrainian cities with some of the largest rocket strikes since the start of the invasion, and as both sides look for ways to break a stalemate on the battlefield.

The cycle of strikes and retaliation is raising fears of escalating civilian casualties in the conflict, which began in February 2022.

On Saturday, Ukraine appeared to have struck back, bombarding Belgorod in an attack that has killed least 22 people and injured nearly 110 others. It was the deadliest single assault against a Russian city since the start of the war.

The Ukrainian government did not comment publicly on the Belgorod attack, as is usually its policy when Russian territory is hit. But an official from Ukraine’s intelligence services, who spoke on the condition of anonymity, said that the strike had been in response to Russia’s massive and deadly air assault against Ukrainian cities on Friday, and that only military facilities had been targeted.

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.”

Mr. Putin had also falsely claimed that Russian strikes only target military facilities.

“We will keep doing it,” he said, referring to the strikes. “We are doing it today, and we will do it tomorrow.”

In the hours leading up to New Year’s Eve, a major holiday both in Russia and Ukraine, Moscow hit the eastern Ukrainian city of Kharkiv, just 60 miles across the border from Belgorod, with missiles and drones. The assault wounded nearly 30 people and severely damaged a hotel, hospitals and residential buildings, according to Ukrainian officials.

The attacks continued on Sunday and Monday, with the Ukrainian Air Force saying that Russia had launched “a record number” of attack drones, an estimated 90 in total, against Ukraine in the early hours of the New Year.

Ukraine said it had shot down all but three of the drones, adding however that falling debris had damaged civilian infrastructure and caused casualties. In the southern port city of Odesa, a frequent target of Russian forces, a 15-year-old boy was killed and seven people injured after debris hit a residential building, local authorities said. In the western city of Lviv, falling debris started a fire in a local museum.

Russia will be held responsible for “all strikes in Odesa, Sumy region, Kyiv, and all our other cities and regions,” President Volodymyr Zelensky of Ukraine said in his nightly address on Saturday, after the attack on Belgorod. He suggested that there would be retaliation for Russian attacks. “Both political and very practical,” he said.