"This is not just another shelling - it is a cynical war crime," Ukraine's National Police said in a post on the Telegram messaging app.
Russia's defence ministry said in a statement that its forces struck a Ukrainian military equipment staging area in the Sumy region with drones, TASS state news agency reported.
Friday's meeting of Russian and Ukrainian officials in Turkey failed to broker a temporary ceasefire. It was the first direct dialogue between the two sides since the early months of the war that Russia launched in February 2022.
Under pressure from US President Donald Trump to end the bloodiest conflict in Europe since World War II, delegates from the warring countries met for the first time since March 2022, the month after Russia invaded its neighbour.
The talks in an Istanbul palace lasted under two hours.
Russia expressed satisfaction with the meeting and said it was ready to continue contacts. Both countries said they had agreed to trade 1000 prisoners of war each in what would be the biggest such exchange yet.
But Kyiv, which wants the West to impose tighter sanctions unless Moscow accepts a proposal from Trump for a 30-day ceasefire, immediately began rallying its allies for tougher action.
As soon as the talks ended, Ukraine's President Volodymyr Zelenskiy held a phone call with Trump and the leaders of France, Germany and Poland, his spokesperson said.
Zelenskiy said robust sanctions should follow if Russia rejected a ceasefire.
Russia's demands were "detached from reality and go far beyond anything that was previously discussed," a source in the Ukrainian delegation told Reuters.
The source, speaking on condition of anonymity, said Moscow had issued ultimatums for Ukraine to withdraw from parts of its own territory in order to obtain a ceasefire "and other non-starters and non-constructive conditions".
British Prime Minister Keir Starmer said the Russian position was "clearly unacceptable" and that European leaders, Ukraine and the US were "closely aligning" their responses.
European Commission President Ursula von der Leyen said the EU was working on a new package of sanctions against Moscow.
Russia's lead negotiator, Vladimir Medinsky, told reporters his team had "taken note" of the Ukrainians' request for direct talks between Zelenskiy and President Vladimir Putin. Putin, after proposing the direct talks, had spurned a challenge from the Ukrainian leader to meet him personally in Istanbul.
Ukrainian Foreign Minister Andrii Sybiha wrote on X that he and EU foreign policy chief Kaja Kallas agreed that "pressure on Moscow must be strengthened to achieve a full and durable ceasefire".
Zelenskiy said Kyiv's top priority was "a full, unconditional and honest ceasefire... to stop the killing and create a solid basis for diplomacy".
The sides mostly repeated known positions. The Ukrainians wanted an immediate ceasefire and talks to ensue, while the Russians demanded more talks before agreeing on a ceasefire.
Expectations for a breakthrough, already low, were dented on Thursday when Trump, winding up a Middle East tour, said there would be no movement until he and Putin met.
Russia says it wants to end the war by diplomatic means and is ready to discuss a ceasefire. But it has raised questions and concerns, saying Ukraine could use a pause to rest its forces, mobilise troops and acquire more Western weapons.
Ukraine and its allies accuse Putin of stalling, and say he is not serious about wanting peace.
