Video footage showed a five-storey block of flats on fire.
Mr Klitschko said medics and rescuers were being scrambled to the scene and a body had been pulled out of one of the buildings.
The attacks come after the biggest Ukrainian victory of the nine-month conflict so far – the withdrawal of Russian troops from the southwestern Kherson region.
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Since Kherson was liberated, Moscow has stepped up its attacks on Ukrainian cities, with Lviv and Kharkiv also reportedly hit on Tuesday.
Despite euphoria among Ukrainians, military analysts and Western allies fear the Kremlin is redeploying its troops to frontlines elsewhere in the country.
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Reports of war crimes and devastating abuse are also beginning to emerge now the Russians have left.
Image: Emergency vehicles outside the building hit in Kyiv
Zelenskyy demands 10-point peace plan
Ukrainian President Volodmyr Zelenskyy addressed the G20 summit in Bali virtually on Tuesday, laying out a 10-point peace plan to end the conflict.
He also stressed he would not agree to the Minsk 3 deal – a series of failed international agreements that tried to end the war in the Donbas.
The plan includes energy security, implementation of the UN charter, and a total withdrawal of Russian troops from the country.
In another G20 meeting, Prime Minister Rishi Sunak called on Russia to “get out of Ukraine and end this barbaric war”, adding that it was “notable” President Vladimir Putin chose not to attend the summit himself, sending his foreign minister Sergei Lavrov instead.
He may not be the one to sit down with Vladimir Putin, but Keith Kellogg, President Trump’s special envoy for Ukraine, summed up the horror of Sunday’s ballistic missile strikes on Sumy succinctly.
“Today’s Palm Sunday attack by Russianforces on civilian targets in Sumy crosses any line of decency,” he said.
“As a former military leader, I understand targeting and this is wrong.”
He does not seem to care if he alienates his US counterpart, who has been strangely predisposed to fawn over him to date.
Perhaps he is raising the stakes as high as he can to illustrate his strength of hand: Strikes on civilians damage Ukrainianmorale – even if they are hardly battlefield wins – and on the battlefield, he is pushing ahead and does not want to stop.
Image: At least 34 people, including two children, were killed in Sumy on Sunday. Pic: Reuters
Perhaps he knows that if he keeps up his military momentum, President Trump will tire of a conflict he realises he cannot solve and let the matter slip while staying true to his MAGA-economic priorities by letting funds for Ukraine dry up.
Perhaps he thinks President Trump is so keen on a rapprochement with Russia, on the big Putin-Trump bilateral, that the details, the civilian deaths along the way, will all be by-the-by when that long-sought photo-op finally happens.
Whatever it is, President Putin seems to be in no rush to get things settled.
His spokesman told a Russian state reporter on Sunday that talks were under way at several levels but that “of course, it is impossible to expect any instant results”.
Withdrawing his troops would get instant results. But that is not what Vladimir Putin wants.
His war economy is working for him, and he has the attention of the one country he considers a worthy adversary, the United States.
In the meantime, this attack reinforces why President Zelenskyy’s plea for air defence systems is his top priority. And why a ceasefire cannot come soon enough.
At least 34 people – including two children – have been killed after a Russian missile attack on a Ukrainian city.
The country’s state emergency service said another 117 people have been injured, with 15 children among them, in the northeastern city of Sumy.
Ukraine’sforeign ministry later added that one of the children injured was a baby girl born this year, saying “even newborns are targets for Russia’s crimes”.
Volodymyr Zelenskyy also shared videos on Telegram of the aftermath of the attack on social media, showing dead bodies in the middle of a city street near a destroyed bus.
Image: Two children were killed in the strike. Pic: State Emergency Service of Ukraine
Russia ‘dragging out this war’ – Zelenskyy
The Ukrainian president said on social media “only scoundrels can act like this” and that “tough reaction from the world is needed”.
“Russiawants exactly this kind of terror and is dragging out this war,” he added. “Without pressure on the aggressor, peace is impossible.
“Talks have never stopped ballistic missiles and air bombs. We need the kind of attitude towards Russia that a terrorist deserves.”
Andriy Kovalenko, a security official who runs Ukraine’s centre for countering disinformation, noted the strike came after a visit to Moscow by US envoy Steve Witkoff.
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From Saturday: Putin meets Trump envoy for talks
US official: ‘This is wrong’
Keith Kellogg, Donald Trump‘s envoy for the Ukraine war, said the attack crosses “any line of decency” and that “there are scores of civilian dead and wounded”.
He added: “As a former military leader, I understand targeting and this is wrong. It is why President Trump is working hard to end this war.”
In response to Mr Kellogg, Mr Zelenskyy’s communications adviser, Dmytro Lytvynm asked: “Don’t you think it’s time to smack the Moscow mule across the nose with a 2X4?”.
Later, US secretary of state Marco Rubio said the strike was “horrifying” and a “tragic reminder of why President Trump and his Administration are putting so much time and effort into trying to end this war and achieve durable peace”.
Image: Pic: AP
UK Foreign Secretary David Lammy added he was “horrified” by Russia’s “barbaric strike” on Sumy, and called for an “immediate ceasefire”.
Meanwhile, EU Commission President Ursula von der Leyen said “cruelty struck again” and called the strike a “blatant violation of international law”.
It came hours before a separate Russian strike killed three people in the central district of the southern city of Kherson.
The local governor, Oleksandr Prokudin, said a 68-year-old woman was injured and died in hospital and that a 48-year-old man also died after “the occupiers dropped an explosive device from a drone”.
A 62-year-old woman was also killed “as a result of the shelling”.
On Saturday, a Russian guided bomb hit a house in the northeastern Ukrainian town of Kupiansk on Saturday, injuring four people.
Governor Oleh Syniehubov said on Telegram that three others could be trapped under rubble.
It comes after Russian diplomats accused each other of violating a tentative US-brokered deal to pause strikes on energy infrastructure.
“The Ukrainians have been attacking us from the very beginning, every passing day, maybe with two or three exceptions,” Sergey Lavrov, Russia’s foreign minister, said, adding that Moscow would provide a list of Kyiv’s attacks from the past three weeks.
Andrii Sybiha, his Ukrainian counterpart, dismissed the claim saying on Saturday that Russia launched “almost 70 missiles, over 2,200 [exploding] drones, and over 6,000 guided aerial bombs at Ukraine, mostly at civilians” since agreeing to the limited pause on strikes.
He may not be the one to sit down with Vladimir Putin, but Keith Kellogg, President Trump’s special envoy for Ukraine, summed up the horror of Sunday’s ballistic missile strikes on Sumy succinctly.
“Today’s Palm Sunday attack by Russianforces on civilian targets in Sumy crosses any line of decency,” he said.
“As a former military leader, I understand targeting and this is wrong.”
He does not seem to care if he alienates his US counterpart, who has been strangely predisposed to fawn over him to date.
Perhaps he is raising the stakes as high as he can to illustrate his strength of hand: Strikes on civilians damage Ukrainianmorale – even if they are hardly battlefield wins – and on the battlefield, he is pushing ahead and does not want to stop.
Image: At least 34 people, including two children, were killed in Sumy on Sunday. Pic: Reuters
Perhaps he knows that if he keeps up his military momentum, President Trump will tire of a conflict he realises he cannot solve and let the matter slip while staying true to his MAGA-economic priorities by letting funds for Ukraine dry up.
Perhaps he thinks President Trump is so keen on a rapprochement with Russia, on the big Putin-Trump bilateral, that the details, the civilian deaths along the way, will all be by-the-by when that long-sought photo-op finally happens.
Whatever it is, President Putin seems to be in no rush to get things settled.
His spokesman told a Russian state reporter on Sunday that talks were under way at several levels but that “of course, it is impossible to expect any instant results”.
Withdrawing his troops would get instant results. But that is not what Vladimir Putin wants.
His war economy is working for him, and he has the attention of the one country he considers a worthy adversary, the United States.
In the meantime, this attack reinforces why President Zelenskyy’s plea for air defence systems is his top priority. And why a ceasefire cannot come soon enough.