Ukrainian President Volodymyr Zelensky has demanded a tough global response to Russia after its forces fired a missile at a crowded train station killing at least 52 people.
Mr Zelensky's voice rose in anger during his nightly address on Friday, when he said the strike on the Kramatorsk train station, where 4,000 people were trying to flee a looming Russian offensive in the east, amounted to another war crime.
Five children were among the dead and dozens of people were severely injured, Ukrainian officials said.
"All world efforts will be directed to establish every minute of who did what, who gave what orders, where the missile came from, who transported it, who gave the command and how this strike was agreed," the president said.
Photos taken after the attack showed bodies covered with tarpaulins and the remnants of a rocket painted with the words "For the children" in Russian.
The Russian phrasing seemed to suggest the missile was sent to avenge the loss or subjugation of children, although its exact meaning remained unclear.
The strike shocked world leaders.
"There are almost no words for it," European Union Commission President Ursula von der Leyen told reporters during a visit to Ukraine. "The cynical behaviour (by Russia) has almost no benchmark any more."
The attack came as workers elsewhere in the country unearthed bodies from a mass grave in Bucha, a town near Kyiv, where graphic evidence of dozens of killings emerged following the withdrawal of Russian forces.
“Like the massacres in Bucha, like many other Russian war crimes, the missile attack on Kramatorsk should be one of the charges at the tribunal that must be held,” Mr Zelensky said.
In footage filmed on mobile phones in the aftermath of the station attack, scenes of panic developed as passengers try to flee the main platform. Lifeless bodies and patches of blood are scattered on the ground in the footage.
In one recording a woman cries: “How many dead bodies? There are children - the children.”
One witness Oleksandr Kachura, who arrived at the station just after the missile had struck, told Sky News: “There were a lot of fire trucks, ambulances, it was chaos, a crush, people running in different directions. Near the entrance, cars were on fire and as far as I know, people died in them. They didn’t have time to get out,” he said.
A 17-year-old called Nastya whose head was bandaged and had wounds on her arm told the broadcaster: ““I remember a really loud noise and there was something landing, shells or rockets. Everybody hit the ground. That’s all, nightmare, everything starts to burn, everyone was panicking.”
A woman called Ludmila had been deeply shaken. “It was terrifying, the horror, the horror, heaven forbid, to live through this again, no, I don’t want to.”
Russia denied it was responsible for the strike and accused Ukraine’s military of firing the missile as a false-flag operation so Moscow would be blamed for civilian deaths.
Ukraine’s state railway company said that residents of the country’s contested Donbas region, where Russia has refocused its forces after failing to take over the Ukrainian capital, Kyiv, could flee through other train stations on Saturday.
“The railways do not stop the task of taking everyone to safety,” the statement on the messaging app Telegram said.
The Ministry of Defence said in the aftermath of the attack, said on Saturday that Russian forces were targeting civilians.
Russia was focusing its offensive, which included cruise missiles launched by its naval forces, on the eastern Donbas region, it said in a daily briefing.
It said it expected air attacks would increase in the south and east as Russia seeks to establish a land bridge between Crimea, which Moscow annexed in 2014, and the Donbas but Ukrainian forces were thwarting the advance.
After failing to take Kyiv in the face of stiff resistance, Russian forces have set their sights on the eastern Donbas region, the mostly Russian-speaking, industrial area where Moscow-backed rebels have been fighting Ukrainian forces for eight years and control some places.
The BBC reported the Kremlin has reorganised its military command to put a general with extensive experience of warfare in Syria in charge of its forces in Ukraine.
General Alexander Dvornikov, commander of Russia’s southern military district, now reportedly leads Moscow’s invasion efforts.
“That particular commander has a lot of experience of Russian operations in Syria. So we would expect the overall command and control to improve,” a Western official told the broadcaster.
However, they added that “unless Russia is able to change its tactics, it’s very difficult to see how they succeed in even these limited objectives that they’ve reset themselves”.
Although the train station is in Ukrainian government-controlled territory in the Donbas, Russia accused Ukraine of carrying out the attack, as did the region's Moscow-backed separatists who work closely with Russian troops.
Western experts, however, dismissed Kremlin spokesperson Dmitry Peskov's assertion that Russian forces "do not use" that type of missile.
A Western official said Russia's forces have used the missile - and that given the strike's location and impact, it was likely Russia's.
Justin Bronk, a research fellow at the Royal United Services Institute in London, added that only Russia would have reason to target railway infrastructure in the Donbas, as it is critical for the Ukrainian military's efforts to reinforce its units.
Mr Bronk pointed to other occasions when Russian authorities have tried to deflect blame by claiming their forces no longer use an older weapon "to kind of muddy the waters and try and create doubt". He suggested Russia specifically chose the missile type because Ukraine also possesses them.
Ukrainian authorities and Western officials have repeatedly accused Russian forces of atrocities in the war that began on February 24.
More than 4 million Ukrainians have fled the country, and millions more have been displaced. Some of the grisliest evidence has been found in towns around Ukraine's capital, Kyiv, from which Russian President Vladimir Putin's troops pulled back in recent days.
In Bucha, Mayor Anatoliy Fedoruk has said investigators found at least three sites of mass shootings of civilians and were still finding bodies in yards, parks and city squares - 90% of whom were shot.
Russia has falsely claimed that the scenes in Bucha were staged.