Two ballistic missiles struck the heart of the city about 10.15am (5.15pm AEST) as people gathered to celebrate Palm Sunday, according to officials.

Videos posted from the scene on official channels showed bodies on the ground amid debris and smoke around central Sumy.

“On this bright Palm Sunday, our community has suffered a terrible tragedy,” acting Mayor Artem Kobzar said in a statement on social media.

“Unfortunately, we already know of more than 20 deaths.”

At least 24 people were killed as a result of the attack, including one child, the State Emergency Service of Ukraine said in a statement. A further 84 people were injured, including seven children, it said.

Ukrainian President Volodymyr Zelenskyy confirmed that rescue efforts were ongoing and said “dozens” had been killed in the double missile attack.

“According to preliminary information, dozens of civilians were killed and wounded. Only filthy scum can act like this — taking the lives of ordinary people,” he said.

Zelenskyy also called for a global response to the attack. “Talks have never stopped ballistic missiles and aerial bombs. What’s needed is an attitude toward Russia that a terrorist deserves,” he said.

The strike came less than a day after Russia and Ukraine’s top diplomats accused each other of violating a tentative US-brokered deal to pause strikes on energy infrastructure, underscoring the challenges of negotiating an end to the three-year-old war.

The two countries’ foreign ministers spoke at separate events at the annual Antalya Diplomacy Forum, a day after US envoy Steve Witkoff met with Russian President Vladimir Putin to discuss peace prospects.

“The Ukrainians have been attacking us from the very beginning, every passing day, maybe with two or three exceptions,” Russian Foreign Minister Sergey Lavrov said, adding that Moscow would provide the US Turkey and international bodies with a list of Kyiv’s attacks during the past three weeks.

His Ukrainian counterpart, Andrii Sybiha, fiercely contested that claim, saying on Saturday that Russia had launched “almost 70 missiles, over 2200 (exploding) drones, and over 6000 guided aerial bombs at Ukraine, mostly at civilians”, since agreeing to the limited pause on strikes.

The attack on Sumy on Sunday was the second large-scale attack to claim civilian lives in just over a week.

It followed a deadly missile strike on Zelenskyy’s hometown of Kryvyi Rih on April 4 that killed some 20 people, including nine children.