Western officials on Friday accused their Russian counterparts of war crimes a day after Russian missiles struck a central Ukrainian city far behind the front lines in an attack Kyiv officials said killed at least 23 people, including three children.

Ukraine said Thursday's strike on Vinnytsia, a city of 370,000 people about 200 kilometers (125 miles) southwest of Kyiv, had been carried out with Kalibr cruise missiles launched from a Russian submarine in the Black Sea.

Russia's Defense Ministry said the cruise missile strike on Vinnytsia was directed at a building where top officials from Ukraine's armed forces were meeting foreign arms suppliers, while Kyiv has denied any military target was hit, saying the attack struck a cultural center used by retired veterans.

"On July 14, Kalibr (cruise) missiles were launched at the House of Officers in Vinnytsia," Russia's Defense Ministry said in its daily update.

"The facility was hosting a conference of the Ukrainian Armed Forces command with representatives of foreign arms suppliers ... The attack resulted in the elimination of the participants."

The attack was the latest in a series of Russian strikes in recent weeks using long-range missiles on crowded buildings in cities far from the front, each killing dozens of people.

Russia denies targeting civilians and said the building it struck on Thursday was used to train troops.

Ukrainian President Volodymyr Zelenskyy called Russia a terrorist state, urged more sanctions against the Kremlin and said the death toll in Vinnytsia could rise.

"Unfortunately, this is not the final number. Debris clearance continues. Dozens of people are reported missing. There are seriously injured (people) among those hospitalized," he said in a video address.

Zelenskyy told an international conference aimed at prosecuting war crimes in Ukraine that the attack had been mounted on "an ordinary, peaceful city."

"No other state in the world poses such a terrorist threat as Russia," he said.

Ukraine's state emergency service said three children, including a 4-year-old girl, were killed in Thursday's attack. Another 71 people were hospitalized and 29 people were missing.

It posted a photograph on its Telegram channel of a toy kitten, a toy dog and flowers lying in the grass. "The little girl Lisa, killed by the Russians today, has become a ray of sunshine," it said. Images of the girl, who had Down Syndrome, pushing a pram like one found in the debris, went viral online.

Authorities in the southern city of Mykolaiv, closer to the front lines, reported fresh Russian strikes on Friday morning, which wounded at least two people.

"This time, they hit Mykolaiv around 7:50 a.m., knowing full well that there were already many people on the streets at that time. Real terrorists!" Mykolaiv mayor Oleksandr Senkevych posted on social media.

G-20 meeting

The Vinnytsia attack overshadowed the start of a meeting of G-20 finance ministers in Indonesia on Friday, where the top U.S. and Canadian representatives accused Russian officials in attendance of culpability in atrocities.

Russia invaded Ukraine on Feb. 24 in what it called a "special operation" to demilitarize and "denazify" its neighbor. U.S. Treasury Secretary Janet Yellen condemned Russia's "brutal and unjust war" and said Russian finance officials shared responsibility.

"By starting this war, Russia is solely responsible for negative spillovers to the global economy, particularly higher commodity prices," she said.

Russian officials participating in the meeting were "adding to the horrific consequences of this war through their continued support of the Putin regime," she added.

"You share responsibility for the innocent lives lost and the ongoing human and economic toll that the war is causing around the world," she said, addressing the Russian officials.

Canadian Finance Minister Chrystia Freeland told Russian officials at the meeting that she held them personally responsible for "war crimes," a Western official told Reuters.

As Russia pressed its offensive in Ukraine's eastern Donbass region, the United States and more than 40 other countries agreed on Thursday to coordinate investigations into suspected war crimes.

Ghost town

The stepped-up Russian attacks on cities far from the front come at a time when momentum appears to be shifting in the near-five-month war after weeks of Russian gains.

After capturing the eastern industrial cities of Severodonetsk and Luhansk in huge battles that killed thousands of troops on both sides, Russia has paused its advance. A Ukrainian general said on Thursday that Kyiv had not lost "a single meter" of territory in a week.

Ukraine has meanwhile unleashed new HIMARS rocket systems received from the United States, striking targets deep in Russian-held territory. It appears to have focused on Russian logistics, blowing up depots of ammunition that Moscow relies on for the massive artillery barrages that accompany its assaults.

Ukraine says it is preparing a counterattack in the coming weeks to recapture a swathe of southern territory near the Black Sea coast, where authorities installed by Moscow say they are planning referendums on joining Russia.

The eastern Ukrainian town of Popasna that fell to Russian forces two months ago is now a ghost town with little sign of life.