* At least 23 killed in Russian attack: Ukrainian officials
* Russia denies targeting civilians
* Yellen slams Russian officials at G20 meeting
* Nations pledge to cooperate on war crimes investigations
A Ukrainian city far from the frontline grieved for its dead and cleared its streets on Friday, a day after a Russian missile attack killed at least 23 people and wounded scores.
Ukraine said Thursday's strike on an office building in Vinnytsia, a city of 370,000 people about 200 km southwest of Kyiv, had been carried out with Kalibr cruise missiles launched from a Russian submarine in the Black Sea.
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.
Residents placed teddy bears and flowers at a makeshift memorial near the site of the strike.
Among the dead was Lisa, a 4-year-old girl with Down's Syndrome, found in the debris next to a pram. Images of her pushing the same pram, posted by her mother on a blog less than two hours before the attack, quickly went viral.
Liza Dmitrieva, a 4 year old who died in a Russian missile strike, is pictured in Vinnytsia, Ukraine. LogoClub Children's Center/Handout via REUTERS
Her severely injured mother, Iryna Dmitrieva, was being kept in an information blackout at a hospital for fear that finding out about her daughter would kill her, doctors said.
"She is suffering from burns, chest injuries, abdominal injuries, liver and spleen injuries. We have stitched the organs together, the bones were crushed as if she went through a meat grinder," Oleksandr Fomin, chief doctor at the Vinnytsia Emergency Hospital, said. Were she told of her daughter's death, "we would lose her".
Rescuers remove debris of the House of Officers building hit by a Russian missile strike, as Russia's attack on Ukraine continues, in Vinnytsia, Ukraine. REUTERS
President Volodymyr Zelenskiy's wife, Olena, tweeted that she recognised the girl, who had once been among a group of disabled children who painted Christmas ornaments with the first lady in a holiday video.
"Look at her, alive, please," Olena Zelenska wrote.
The building housed an officers' club, which Russia's defence ministry said was being used for a meeting between military officials and foreign arms suppliers. It added: "The attack resulted in the elimination of the participants."
Ukraine said the club functioned as a cultural centre. The building also housed shops, commercial offices and a concert hall, where musicians were rehearsing for a pop concert planned for that night. A nearby medical centre was also destroyed.
Zelenskiy 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 hospitalised,” he said in a video address to an international conference aimed at prosecuting war crimes in Ukraine.
Authorities in the southern city of Mykolaiv, closer to the frontlines, reported fresh Russian strikes on Friday morning which wounded at least two people. They released video pictures of firefighters battling the blaze in the rubble.
"This time, they hit Mykolaiv around 7:50am, 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.
Despite the bloodshed, both sides have described important progress in recent days towards an agreement that would lift a blockade that has restricted the export of Ukrainian grain. Mediator Turkey has said a deal could be signed next week.
Asked if that timeline was realistic, a senior Ukrainian official told Reuters: "We really hope so. We're hurrying as fast as we can." The source asked not to be identified.
Russia's defence ministry said Moscow's proposals were "largely supported" by the negotiators and an agreement on the grain shipments was close.
A deal would probably involve inspections of vessels to ensure Ukraine was not bringing in arms, and guarantees from Western countries that Russia's own food exports are exempt from sanctions.
Moscow welcomed a written clarification issued by Washington on Thursday that banks, insurers and shippers would not be targeted by sanctions for facilitating shipments of Russian grain and fertilizer.
The war dominated the agenda at a meeting of G20 finance ministers in Indonesia on Friday. The conflict involving two of the world's top grain exporters and one of its main oil and gas producers is causing global shortages of food and energy, inflation, financial crisis and, potentially, hunger.
"By starting this war, Russia is solely responsible for negative spillovers to the global economy, particularly higher commodity prices," US Treasury Secretary Janet Yellen said.
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.
Russia sent a deputy finance minister to the meeting, with Finance Minister Anton Siluanov participating remotely. When G20 foreign ministers met last week, Russia's Sergei Lavrov walked out after facing what he called "frenzied criticism".
Russia calls its intervention a "special military operation" to disarm Ukraine and root out nationalists. Kyiv and its allies call it an attempt to reconquer a country which broke free of Moscow's rule in 1991.
Russian-backed separatists in eastern Ukraine said a British man in their custody had died of health problems. The separatists, who captured Paul Urey, 45, in April, had accused him of being a mercenary. A British relief group, Presidium Network, described him as a humanitarian volunteer.
The stepped-up Russian attacks on cities far from the front come at a time when momentum appears to be shifting after weeks of Russian gains.
Since capturing the eastern industrial cities of Sievierodonetsk and Lysychansk in battles that killed thousands of troops on both sides, Russia has paused its advance. A Ukrainian general said on Thursday Kyiv had not lost "a single metre" 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 counter-attack in coming weeks to recapture a swath of southern territory near the Black Sea coast.
