Two Russian ballistic missiles slammed into a bustling city center in northeastern Ukraine on Sunday morning, officials said, killing at least 32 people in what appeared to be the deadliest attack against civilians this year.

The midmorning strike on the city of Sumy was the latest in a string of intensifying Russian attacks on urban centers in Ukraine that have inflicted heavy civilian casualties despite the Trump administration’s push for a cease-fire.

Officials said the city center was crowded with civilians out enjoying Palm Sunday, a Christian celebration popular in Ukraine, when the missiles hit. Lively streets were turned into scenes of carnage: Video of the aftermath showed mangled and bloodied bodies laying motionless, burning cars and debris covering the road as screams and sirens wailed in the background.

Two children were among the dead and at least 99 people were wounded, according to Ukraine’s emergency services.

“People were harmed right in the middle of the street — in cars, on public transport, in their homes,” the interior minister, Ihor Klymenko, lamented on social media.

The strikes came just over a week after a Russian missile hit near a playground in the central city of Kryvyi Rih, killing 19 people, including nine children. In that attack and in the one on Sunday, according to Ukrainian officials, Russia used ballistic missiles, which travel at high speeds, making them very difficult to shoot down.

Overall, civilian deaths have increased since U.S.-mediated cease-fire talks began in March. The United Nations said last week that 164 civilians were killed in Ukraine last month, a 50 percent increase from February and 70 percent more than the same period a year earlier.

President Volodymyr Zelensky of Ukraine — who has accused Russia of using the cease-fire talks to stall for time — said the attack on Sumy showed that Moscow had no real interest in a cease-fire despite the Trump administration’s efforts to broker one.

“A strong reaction from the world is needed. From the United States, from Europe, from everyone in the world who wants this war and the killings to end,” Mr. Zelensky said in a message posted on Telegram. “Russia seeks exactly this kind of terror and is dragging out the war.”

Both Russia and Ukraine have pledged to halt attacks on energy infrastructure, only to accuse each other of violations. Kyiv and Moscow have also agreed to a cease-fire on the Black Sea, but a deal has yet to come into effect. Russia has also rejected a full, unconditional 30-day cease-fire that Ukraine had accepted at the urging of the United States.

Ukraine’s foreign minister, Andrii Sybiha, said on Saturday that since cease-fire talks began last month in Saudi Arabia, Russia “only escalated its attacks on Ukrainian civilian objects and increased missile terror, including strikes on energy facilities.”

“This is Russia’s response to all peace proposals,” Mr. Sybiha told the state news agency Ukrinform. “They delay, manipulate, and play with their partners to continue aggression.”

Ukraine’s allies echoed those sentiments on Sunday in what appeared to be a coordinated response to condemn the strike on Sumy.

“Everyone knows: this war was initiated by Russia alone. And today, it is clear that Russia alone chooses to continue it — with blatant disregard for human lives, international law, and the diplomatic efforts of President Trump,” President Emmanuel Macron of France said on social media.

There was no immediate comment from Russia’s military about the attack on Sumy, located just 18 miles from the Russian border. Before the war, the city was home to about 250,000 people. It has since become a refuge for Ukrainian civilians fleeing villages and towns along the Russian border to escape bombardment and potential assaults.

Sumy and its surrounding region have regularly come under Russian attack over the past year, particularly since Ukraine used the area as a base for a cross-border offensive into Russia’s neighboring Kursk region. Moscow’s forces pushed most Ukrainian troops out of Kursk this year, but Kyiv has warned that Russia is preparing to push into the Sumy region and open a new front in the war.

Valeria Voronenko, a 24-year-old Sumy resident, rushed to the scene of the strike on Sunday. She said she had seen one woman running around, searching for her mother, and another clutching a crying child — both with bloodied faces.

“The whole atmosphere — people shouting, crying,” she said. “It was chaos.”

Ms. Voronenko said locals had grown accustomed to attacks and the buzz of Russian drone flying overhead, but that Sunday’s assault was “the worst tragedy” the city had experienced over three years of war.

“We’re hoping for negotiations,” she said, “for everything to end.”