Russia has denied attacking a Ukrainian maternity hospital, branding horrific video of the aftermath and reports of the destruction as "fake news" and "information terrorism".
Ukrainian authorities have said three people, including a child, died when the children's and maternity hospital in the southern city of Mariupol was bombed on Wednesday.
President Volodymyr Zelenskyy said the target on the hospital was the "ultimate proof that what is happening is the genocide of Ukrainians".
But Russia's first deputy permanent representative to the United Nations, Dmitry Polyanskiy, claimed the building was no longer a maternity hospital and had been taken over by Ukrainian troops.
"That’s how fake news is born," he tweeted.
Polyanskiy said Russia had warned on 7 March that the hospital had been turned into a military object from which Ukrainians were firing.
Russian foreign ministry spokeswoman Maria Zakharova echoed his claims and said reports of Russia bombing the hospital was fake and amounted to "information terrorism".
Deputy mayor Sergei Orlov said 17 others had been injured in the attack, including pregnant women.
He told the BBC: "I'm absolutely sure they know about this facility and this is their third hospital that they are destroying in this city.
"I'm absolutely sure (these are their) targets."
Rescuers worked through the night to free pregnant women from the rubble as temperatures dropped below -4C, sparking fears for those who have been pinned under the wreckage.
The Ukrainian Red Cross warned the strike would likely cause a complete collapse of paediatric care in Mariupol.
Footage and images from inside the wrecked health centre showed much of the hospital's equipment and the paediatric care wards were reduced to ashes.
Watch: Mariupol hospital heavily damaged after suspected Russian attack
Vladimir Putin ordered his troops in to invade 15 days ago, causing the biggest humanitarian crisis since World War Two as more than 2 million refugees flee Ukraine for neighbouring countries.
In a statement released from the Presidential Palace in Kyiv, Zelenskyy said: "Europeans, you can't say you didn't see what is happening. You have to tighten the sanctions until Russia can't continue their savage war.
"What kind of country bombs hospitals? Is afraid of hospitals? Of a maternity ward?
"Was someone insulting Russians? Were pregnant women shooting in direction of Rostov? Was it the ''denazification'' of a hospital? What the Russians did at Mariupol was beyond savagery."
Mariupol has been under siege from Russian forces for over a week, with its residents cut off from food, water, electricity and vital medicines.
Mass graves have been dug as people die from thirst, as Mariupol mayor Vadim Boychenko said a six-year-old girl called Tanya had died "alone, exhausted, frightened, terribly thirsty."
It comes amid fears in Britain and the US that Putin could be setting the stage to use chemical weapons in Ukraine after the Kremlin made unfounded allegations the US had been supporting a bioweapons programme.
White House press secretary Jen Psaki said that Russia had been making “false claims about alleged US biological weapons labs and chemical weapons development in Ukraine”.
She added those allegations had been echoed in Beijing.
“Now that Russia has made these false claims, and China has seemingly endorsed this propaganda, we should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them,” she tweeted.