Ukraine's President Volodymyr Zelensky has invited Donald Trump to visit his country ahead of any deal with Russia to end the war.
"Please, before any kind of decisions, any kind of forms of negotiations, come to see people, civilians, warriors, hospitals, churches, children destroyed or dead," Zelensky said in an interview for CBS's 60 Minutes programme.
The interview was recorded before a Russian missile hit the city of Sumy, killing 34 people and injuring 117 others.
Russia has not commented. Trump said he had been told it was a mistake, without specifying whether this admission came from Moscow. Germany's chancellor-in-waiting, Friedrich Merz, accused Russia of committing a war crime.
The attack comes as the US, Ukraine's strongest military ally, has been pursuing an end to the war - now in its fourth year - through negotiation under Trump.
Asked about the attack, the US president said it was "terrible" and that he had been "told they made a mistake", but did not elaborate.
Earlier, Trump's special envoy to Ukraine, retired Lt-Gen Keith Kellogg, said the attack had crossed "any line of decency".
However, it remains to be seen if Trump will accept Zelensky's invitation.
Scott Bessent, the US treasury secretary, is the only senior member of Trump's team to visit Kyiv, and that was to demand Zelensky sign a contract heavily weighted in Washington's favour to trade Ukraine's mineral wealth for continued military aid. Zelensky refused.
The Ukrainian president has highlighted Russia's continued attacks on civilians while Trump attempts to improve relations with Moscow in search of a ceasefire.
US special envoy Steve Witkoff has already held three meetings with Vladimir Putin, and Kyiv is adamant Moscow will exploit this as it continues to erode Ukraine's territory.
European leaders condemned the Sumy attack. Merz, who is expected to take over as Germany's new chancellor next month, told the country's public broadcaster ARD that the attack constituted a "serious war crime".
"It was a perfidious act.. and it is a serious war crime, deliberate and intended," the conservative politician said.
Germany's outgoing Chancellor Olaf Scholz, meanwhile, said the attack showed "just what Russia's supposed readiness for peace [was] worth".
French President Emmanuel Macron accused Russia of "blatant disregard of human lives, international law, and the diplomatic efforts of President Trump".
"Strong measures are needed to impose a ceasefire on Russia," he said. "France is working tirelessly toward this goal, alongside its partners."
Describing the attack as "barbaric", European Commission President Ursula von der Leyen added: "Russia was and remains the aggressor, in blatant violation of international law.
"Strong measures are urgently needed to enforce a ceasefire. Europe will continue to reach out to partners and maintain strong pressure on Russia until the bloodshed ends and a just and lasting peace is achieved, on Ukraine's terms and conditions."
British Prime Minister Sir Keir Starmer also gave a view, saying he was "appalled at Russia's horrific attacks on civilians in Sumy".
Getty ImagesA spokesperson for UN Secretary-General António Guterres said he was "deeply alarmed and shocked" to learn of the missile attack.
"Attacks against civilians and civilian objects are prohibited under international humanitarian law, and that any such attacks, wherever they occur, must end immediately", he added.
Guterres stressed the UN's support for "meaningful efforts towards a just, lasting and comprehensive peace that fully upholds Ukraine's sovereignty, independence and territorial integrity".
Sunday's double missile strike was the deadliest attack on civilians in Ukraine this year.
Another Russian missile attack, earlier this month on 4 April, killed 20 people and injured 61 in the city of Kryvyi Rih.
On that occasion, Russia's defence ministry said it had targeted a meeting of "unit commanders and Western instructors" in a restaurant. No evidence was provided.
It is estimated that hundreds of thousands of people - the vast majority of them soldiers - have been killed or injured on all sides since Russia launched a full-scale invasion of Ukraine on 24 February 2022.
The UN estimates that nearly seven million Ukrainians are currently living as refugees.
The conflict goes back more than a decade, to 2014, when Ukraine's pro-Russian president was overthrown. Russia then annexed the Black Sea peninsula of Crimea and backed insurgents in bloody fighting in eastern Ukraine.
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