KYIV: Ukrainian authorities said Sunday that Russia had bombed a school sheltering 400 people in the besieged port of Mariupol, as Moscow announced it had again fired hypersonic missiles in Ukraine.

The claim to have used the next-generation weapon on its neighbour for a second time came as China's ambassador to the US said his country was not sending weapons to Russia for use in Ukraine, but did not definitively rule it out.

Turkey said the two sides were close to a deal to stop the fighting, amid reports of more civilians being killed in strikes across the country.

Ukrainian President Volodymyr Zelensky said the siege of Mariupol, a strategic mostly Russian-speaking port in the southeast where utilities and communications have been cut for days, would go down as a war crime.

"Our cities have turned into multi-storey ruins, every area is like a horror movie," Sergiy Gaiday, head of the Lugansk regional administration, wrote on the Telegram messaging app.

The war in Ukraine, which Russian President Vladimir Putin launched on February 24, has sparked the fastest growing refugee crisis in Europe since World War II, dragged Russia-West relations down to Cold War-era lows, and is wreaking havoc on the world economy.

'Madman of a leader'

"Yesterday, the Russian occupiers dropped bombs on art school No 12," the Mariupol city council said on Telegram Sunday. Around 400 women, children and elderly people had been sheltering there from bombardments, it added.

The building had been destroyed, said the statement. "Peaceful civilians are still under the rubble."

City authorities also claimed that some residents of Mariupol were being forcibly taken to Russia and stripped of their Ukrainian passports.

"The occupiers are sending the residents of Mariupol to filtration camps, checking their phones and seizing (their) Ukrainian documents," Pavlo Kyrylenko, head of the Donetsk regional administration said. More than 1,000 Mariupol residents had been deported, he added.

"I appeal to the international community: put pressure on Russia and its madman of a leader," he said on Facebook.

A group of children stuck in a clinic in Mariupol for weeks had been taken to Russian-controlled Donetsk, a carer and a relative of a clinic worker told AFP.

In the encircled northern city of Chernigiv, Mayor Vladislav Atroshenko said on television early Sunday that dozens of civilians had been killed after shelling hit a hospital. The city was "suffering from an absolute humanitarian catastrophe", he added.

Hypersonic missile used again

Russia's defence ministry said Moscow had again fired its newest Kinzhal (Dagger) hypersonic missile, destroying a fuel storage site in the southern Mykolaiv region.

The strike would mark the second time the sophisticated weapon has been used in combat, a day after Russia said it used it to destroy an underground arms storage site in western Ukraine, close to the border with NATO member Romania.

The Pentagon hit back, saying Moscow claiming it used a hypersonic missile in Ukraine was a way to reclaim war momentum and that the weaponry was not a "game changer".

In Kyiv, where Russian forces are trying to encircle the capital, a shell exploded outside a ten-storey apartment block, blowing out all the windows and injuring five people.

Humanitarian conditions continued to deteriorate in the mostly Russian-speaking south and east of the country, where Russian forces have been pressing their advance, as well as in the north around the Kyiv.

Aid agencies have warned they are struggling to reach hundreds of thousands of people trapped by the invading Russian forces.

'Hell'

The port of Mariupol has been one of the worst-hit cities as it occupies a key strategic position -- its capture would link the Crimean peninsula, which Russia seized from Ukraine in 2014, with the separatist eastern regions of Donetsk and Lugansk, which broke away the same year and are controlled by Moscow-backed rebels.

Thousands of civilians are thought to be trapped inside the city, where communications, water, electricity and gas have been cut. Russia said on Saturday it had broken through the city's defences and its troops were inside.

Last Wednesday, a theatre where more than 1,000 people had sheltered, was hit, with hundreds still presumed missing in the rubble.

"This is no longer Mariupol, it's hell," said resident Tamara Kavunenko, 58. "The streets are full with the bodies of civilians."

In his daily video message, Zelensky said the Mariupol siege "is a terror that will be remembered even in the next century".

The Ukrainian president, who has gained world-wide fame and admiration for staying in his capital in the face of the Russian advance, warned the Russian people that around 14,000 of their servicemen had been killed.

"And (the number of) victims will only continue to rise," he warned.

The latest toll provided by Russia in early March said nearly 500 servicemen had been killed. The latest toll provided by Ukraine on March 12 said some 1,300 Ukrainian troops had died.

Ukraine has not been providing a civilian toll, except for children, at least 115 of whom have died since the start of the war, according to new figures.

The country's outmanned and outgunned military has put up an unexpected and fierce resistance that has slowed Russia's advance.

10 million flee homes

Aid agencies are struggling to reach people trapped in cities ringed by Russian forces, where the UN says the situation is "dire".

Around 10 million people inside Ukraine have fled their homes to escape the fighting, the head of the UN refugee agency said.

More than 3.3 million of them have fled abroad, while a further estimated 6.5 million have been displaced inside the country, according to the UN.

A Russian editor who risked prison to protest live on the television station she worked for told US media she wanted others to speak out against this "gruesome war".

Turkey says deal is close

Turkey, which has tried to position itself as a mediator in the war because of strong ties to both Russia and Ukraine, said the two sides were making progress in their talks to stop the war.

"We see that the parties are close to an agreement," Foreign Minister Mevlut Cavusoglu said Sunday.

In an interview with daily Hurriyet, presidential spokesman Ibrahim Kalin said the sides were negotiating six points: Ukraine's neutrality, disarmament and security guarantees, so-called "de-Nazification", and the status of the Russian language, the breakaway Donbas region and annexed Crimea.

Economic effects to last 'for months'

Russia's war has been widely condemned around the world and has sparked an unprecedented wave of Western sanctions against Putin, his entourage and Russian companies.

Western businesses from oil companies to fast food franchises have either pulled out or halted operations in Russia, the assets of Russia's Central Bank held abroad have been frozen and many Russian banks have been cut off from the SWIFT system that enables inter-bank transactions.

France said Sunday it had seized 850 million euros ($920 million) of Russian oligarchs' assets on its soil.

The war has sparked turmoil for the world economy as it recovers from the coronavirus pandemic.

Russia is a major exporter of oil, gas and commodities, while Ukraine also is a major supplier of wheat.

As a result, commodity prices have rocketed on supply fears, fuelling inflation that was already at multi-decade highs, the chief economist with the European Bank for Reconstruction and Development told AFP.

"Even if the war stopped today, the consequences of this conflict would be felt for months to come," Beata Javorcik said.