Russia stands accused of carrying out an “atrocity” after an airstrike completely destroyed a maternity hospital in the besieged city of Mariupol, leaving children trapped under rubble as well as doctors and women in labour among the wounded.

       Young girls and boys were said to be buried under the rubble following the bombing, with rescue workers frantically digging to get them out amid fears that further military strikes may take place.

       On a day when Moscow was accused of committing war crimes in Ukraine, the attack left at least 17 people injured. It took place during an agreed ceasefire period meant to allow civilians to evacuate the surrounded southeastern city, where officials say some 400,000 people are being held “hostage” by Russian forces.

       Mariupol has been besieged for days, leaving thousands of people without power, sanitation and basic necessities for almost a week, as it comes under constant bombardment. Bodies have been left lying in the street and fires burn across the city.

       Ukraine’s president Volodymyr Zelensky wrote on Twitter that the hospital attack had left people, including children and trapped under the wreckage and called it an “atrocity”. Authorities said they were trying to establish how many people had been killed or wounded.

       Recommended Ukraine news live: Children’s hospital ‘destroyed’ by explosion Why has Russia invaded Ukraine? The conflict explained Sign The Independent’s petition to help the people of Ukraine

       This map shows the extent of Russia’s invasion of Ukraine

       (PA)

       Video shared by the president showed cheerfully painted hallways strewn with twisted metal and room after room with blown-out windows. Floors were covered in debris.

       The attack prompted Zelensky to repeat calls for a no-fly zone over Ukraine.

       “How much longer will the world be an accomplice ignoring terror? Close the sky right now! Stop the killings! You have power but you seem to be losing humanity,” he wrote.

       Mariupol’s city council said on its social media site that the damage was “colossal.”

       The bombing of the 700-bed hospital came during days of intense bombing on the city. Mariupol’s deputy mayor, said 1,170 residents had died. Around 50 of the dead were buried in a mass grave with mortuaries unable to operate fully.

       “It’s medieval. It’s pure genocide. The attack isn’t simply treacherous. It’s a war crime. They are attacking us with aviation, shells, multiple rocket launchers.” said Sergei Orlov. “We can’t understand how it is possible in the modern world to bomb a hospital for children.”

       Viktor Bondarenko, who fled Mariupol with his family spoke of his fears for his cousin Iryna who worked at the hospital, told The Independent:“We think she is alright, but that is just second-hand information,” he said from Mykolaiv, where he had taken refuge. “But we do not know and we’re very, very worried, we cannot believe anyone would want to kill children."

       Another resident of Mariupol told The Independent: “I don’t have words, it’s terrible. The destruction of civilian infrastructure cannot be allowed in any conflict.”

       He added that all children’s medical services in the city had collapsed and that the situation in Mariupol was “the most critical” in Ukraine.

       The attack on the hospital was condemned internationally, with British Prime Minister Boris Johnson saying: “ There are few things more depraved than targeting the vulnerable and defenceless. The UK is exploring more support for Ukraine to defend against airstrikes and we will hold Putin to account for his terrible crimes.”

       The White House, in response to the attack, said it was “horrifying” to see military force used against innocent civilians.

       Kremlin spokesperson Dmitry Peskov, asked about the hospital, said: “Russian forces do not fire on civilian targets.”

       The airstrike came on a day of increasing concern over Russia’s conduct in the war, which it began when it invaded Ukraine exactly two weeks ago.

       Britain’s Ministry of Defence said Russia had admitted using thermobaric weapons and the United States said Moscow was using “dumb bombs” - unguided munitions with no target.

       At the same time, western officials said they had “serious concerns” that Vladimir Putin might sanction the use of chemical weapons as Russia’s military forces remain bogged down.

       Asked about the use of chemical weapons, a Western official said: “I think we’ve got good reason to be concerned about the possible use of non-conventional weapons, partly because we’ve seen what has happened in other theatres - for example in Syria - partly because we see a bit of setting the scene for that in the sort of false flag claims that are coming out, and some other indications.

       “It’s a serious concern for us.”

       The US Secretary of State compared the assault on Ukraine to the Blitz on Britain during the Second World War, as he received foreign secretary Liz Truss in Washington.

       Elsewhere, there were fresh concerns over the safety of the Chernobyl nuclear plant. Ukraine’s state power operator warned that Russian forces had disconnected the Chernobyl nuclear plant from the grid, sparking fears over the cooling of spent fuel.

       Energoatom said radioactive substances could be released into the air if power is not restored soon.

       Work to repair the connection, which has been occupied by Russian troops for several days, has not been possible because fighting is under way, it said.

       Recommended Putin the imperialist: Why Ukraine is part of his dream of a Greater Russia Ukraine: Children’s hospital ‘completely destroyed’ by Russian bombs in Mariupol Ukraine war in numbers: How many people killed and how many refugees in Russian invasion

       The unfolding humanitarian disaster across Ukraine also gathered pace Wednesday.

       Authorities announced new cease-fires Wednesday morning to allow thousands of civilians to escape from towns around Kyiv as well as Enerhodar, Volnovakha, Izyum and Sumy.

       Previous attempts to establish safe evacuation corridors largely failed because of what the Ukrainians said were Russian attacks. It was not immediately clear whether anyone was able to leave cities on Wednesday, but people streamed out of Kyiv’s suburbs, many headed for the city centre.

       The United Nations estimates more than 2 million people have fled the country, the biggest exodus of refugees in Europe since the end of the Second World War.