Russia accused Ukraine on Saturday of conducting a "terrorist attack" on civilians in Belgorod and using widely prohibited cluster munitions, making the claim during an emergency meeting of the UN Security Council requested by Moscow.
Russia said Ukraine attacked the city of Belgorod with missiles and rockets, killing at least 21 people and wounding dozens more, including 17 children, according to local authorities.
It was "a terrorist attack by the Kyiv regime against a civilian city," Russia's ambassador to the UN Vasily Nebenzya said.
"In order to increase the number of casualties of the terrorist attack they used cluster munitions," he continued, claiming that Kyiv targeted a sports center, an ice rink and a university.
"(It was a) deliberate, indiscriminate attack against a civilian target."
"UN Security Council members have an opportunity to do their duty and assess the damage done to a Russian city, Belgorod," Nebenzya added, holding up a QR code linking to what he said was video of the attack's aftermath.
Ukrainian allies quickly retorted, saying Russia had started the war.
Ukraine's ambassador to the UN Serhii Dvornyk said that "as long as this war, unleashed by the Kremlin dictator, endures the toll of death and suffering will continue to grow."
"As Ukraine is still recovering from yesterday's horrendous strikes, new raids of Russian terror persist. Just hours ago... Russia again terrorized Kharkiv with its S-300 missiles hitting a residential area."
The US representative John Kelly also put the blame squarely on Russian President Vladimir Putin.
"This is (Putin's) war, it is his choice," he said.
"Russia could end this war today... We call for the protection of all civilians on all sides of every conflict."
The British envoy Thomas Pipps said London "deeply" regrets any civilian losses, but also called out Moscow for having started the war with an invasion two years ago.
"There are hundreds of thousands of Russian soldiers in Ukraine. There is not a single Ukrainian soldier in Russia," he said.
"If Russia wants someone to blame for the deaths of Russians in this war, it should start with President Putin."
Phipps likewise said that Russia was the side to blame for targeting non-combatants, saying: "After having failed to to defeat Ukraine militarily, Russia has now turned to indiscriminate attacks on civilians."
The French envoy Nicolas de Riviere said Ukraine was simply defending itself under UN laws, while Moscow was "trampling" over the UN Charter.
Ukraine, which has been resisting a Russian invasion for nearly two years and earlier this week came under a huge Russian missile and drone assault, has not officially commented on the strike against Belgorod.
Belgorod lies about 30 kilometers (19 miles) from the border with Ukraine and has been repeatedly struck by what Moscow says is indiscriminate shelling by Kyiv's forces.
"As the war continues we will see more Ukrainian and Russian civilians killed," said UN assistant secretary-general Mohamed Khiari, warning there were "very real dangers of escalation and spillover of this war."
Unverified footage showed a street strewn with debris and smoke billowing from burnt-out cars in the city's center, while a large blast could be heard on dashcam footage posted on social media.
AFP was not able to immediately verify the circumstances of the strike, one of the deadliest on Russian soil since Moscow launched hostilities against Ukraine in February 2022.
Two Vilkha missiles and Czech-made rockets were used in the attack, Russia said.
