The attack, which authorities said injured women in labour and left children in the wreckage, is the latest grim incident of the 14-day invasion, the biggest assault on a European state since 1945.

The destruction took place despite a Russian pledge to halt firing so at least some trapped civilians could escape the city, where hundreds of thousands have been sheltering without water or power for more than a week.

Kremlin spokesman Dmitry Peskov said: “Russian forces do not fire on civilian targets.” Russia calls its incursion a “special operation” to disarm its neighbour and dislodge leaders it calls “neo-Nazis”.

Ukraine’s foreign ministry posted video of the badly damaged hospital. Huge piles of smouldering rubble littered the scene.

“It is horrifying to see the type of the barbaric use of military force to go after innocent civilians in a sovereign country,” White House press secretary Jen Psaki said.

UN human rights body spokeswoman Liz Throssell said “the incident adds to our deep concerns about indiscriminate use of weapons in populated areas and civilians trapped in active hostilities in numerous areas”.

The Donetsk region’s governor said 17 people were wounded in the incident.

Ukraine accused Russia of breaking the ceasefire around the southern port.

“Indiscriminate shelling continues,” Foreign Minister Dmytro Kuleba wrote on Twitter.

Ukraine said 67 children had been killed across the country since the invasion and at least 1170 civilians had died in Mariupol.

Russia’s defence ministry blamed Ukraine for the evacuation’s failure.

Local officials said some civilians had left several Ukrainian cities through safe corridors, including out of Sumy in the east and Enerhodar in the south, but Russian forces were preventing buses from evacuating civilians from Bucha, a town outside the capital Kyiv.

Russian Foreign Minister Sergei Lavrov arrived in Turkey for talks on Thursday with Kuleba as diplomatic efforts continue.

Ukraine wants a ceasefire, its territories liberated and to resolve all humanitarian issues, Kuleba said, adding: “Frankly … my expectations of the talks are low.”

Moscow wants its demands, including that Kyiv takes a neutral position and drops aspirations of joining the NATO alliance, to be met for it to end its assault.

Kyiv and its Western allies say Russia is inventing pretexts to justify an unprovoked war. Russian President Vladimir Putin has called Ukraine a US colony with a puppet regime and no tradition of independent statehood.

The humanitarian toll, including more than two million refugees from Ukraine, continues to grow since the invasion began on February 24.

Russian forces hold territory along Ukraine’s northeast border, the east and the southeast. Fighting has taken place in the outskirts of Kyiv, while Kharkiv is under bombardment.

A Russian assault force is stalled north of Kyiv and Western countries say the Kremlin has had to adjust its plan to swiftly topple the government in the face of fierce resistance.

Ukrainian authorities are concerned for safety at Chernobyl, the mothballed site of the world’s worst nuclear disaster in 1986, where they said a power cut caused by fighting meant spent nuclear fuel could not be cooled. Russia blames Ukraine for the power cut.

Kuleba said reserve diesel generators had a 48-hour capacity. After that, cooling systems for the spent nuclear fuel would stop, “making radiation leaks imminent”.

The International Atomic Energy Agency said the heat from the spent fuel and the volume of cooling water were such that it was “sufficient for effective heat removal without need for electrical supply”.

The war has brought Russia economic isolation as governments imposed heavy sanctions and businesses shut operations. The World Bank says Moscow is edging close to defaulting on its debt.

Putin’s government took more measures to shore up the economy and said it would respond to a US ban on its oil and energy exports as the rouble dropped to record lows.