A rocket attack on a train station in central Ukraine as the country marked its Independence Day has killed 25 people.
President Zelenskyy had warned for days that Russian forces might attempt “something particularly cruel” this week.
The lethal attack hit the town of Chaplyne in the central Dnipropetrovsk region, he told a meeting of the UN Security Council.
Ukraine had been bracing for especially heavy attacks surrounding the national holiday that commemorates Ukraine’s declaration of independence from the Soviet Union in 1991, which this year fell on the six-month point of the 2022 Russian invasion.
People stand next to a residential house destroyed by a Russian military strike in Chaplyne
It comes as Prime Minister Boris Johnson visited the Ukrainian capital Kyiv again, where he was presented with The Order of Liberty, Ukraine’s highest award which can be bestowed on foreign nationals.
Making his last trip to the country before leaving office, Mr Johnson set out a further £54m of military aid, including drones to target Russian forces.
“What happens in Ukraine matters to us all,” Mr Johnson said on Twitter.
“That is why I am in Kyiv today. That is why the UK will continue to stand with our Ukrainian friends.
“I believe Ukraine can and will win this war.”
Read more: No city has been hit as hard and often as Mykolaiv – and it could get worse
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Boris Johnson walks through Kyiv
The latest package of support for Ukraine includes unmanned surveillance and missile systems as well as 2,000 state-of-the-art drones and anti-tank loitering munitions.
Also included are 850 hand-launched Black Hornet micro-drones, which can be used to provide live feeds and still images to troops.
During his Ukraine visit Mr Johnson also suggested that high energy bills are something UK households must endure as part of the effort to resist Vladimir Putin.
He said “if we’re paying in our energy bills for the evils of Vladimir Putin, the people of Ukraine are paying in their blood.”
What is likeliest outcome in Ukraine and what would tip NATO into conflict? Your question answered