Russian troops stepped up their bombardment of the beleaguered port city of Mariupol in Ukraine on Sunday, shelling an art school where authorities say 400 people had taken refuge.

Hours after the strike, Russia demanded that Ukrainians in the besieged city lay down their arms in exchange for safe passage out of the city. Ukrainian leaders quickly rejected the offer.

Mariupol continues to support part of the the greatest suffering of war. On Sunday, Ukrainian President Volodymyr Zelensky accused Russia of war crimes over its siege, describing the attack on the city as “a terror that will be remembered for centuries”. In his nightly address to the nation, Zelenskyy said Ukraine was interested in peace and that ongoing talks with Russia were “necessary”.

Here are some key things to know about the conflict:

What’s going on in Mariupol?

Mariupol, a strategic port on the Sea of ​​Azov, has been surrounded by Russian troops – cut off from energy, food and water supplies since the early days of Russian President Vladimir’s invasion of Ukraine Putin launched on February 24. Civilian life has been relegated to bomb shelters, with aid groups saying the city faces a humanitarian crisis. Russian forces have also cut off its access to the Sea of ​​Azov.

Civilians trapped in the city of Mariupol under Russian attacks are evacuated in groups under the control of pro-Russian separatists, via other cities, in Mariupol, Ukraine, March 20, 2022. (Photo by Stringer/Anadolu Agency via Getty Images)

An adviser to the Ukrainian president said there was no immediate military aid for Mariupol, saying the closest forces able to help were already battling Russian forces at least 100 kilometers (60 miles) away. Pitched battles continue around the Azovstal steelworks, one of the largest in Europe.

A special forces unit of Ukraine’s National Guard said four Russian navy ships shelled the Sea port of Azov on Sunday, part of the Russian military’s efforts to “cynically destroy the Ukrainian city using all the arsenal at her disposal”. There was no immediate word on the casualties of this incident.

In a statement, the Mariupol city council said Russian soldiers had forced several thousand residents – mostly women and children – to leave and be relocated to Russia. He did not specify where in Russia, and the AP could not immediately confirm the claim.

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The city council said on Sunday that nearly 40,000 people have used their own vehicles to leave the city via a humanitarian corridor over the past week, nearly 10% of its 430,000 population. Other fleeing residents arrived by train on Sunday in Lvov.

And the art school?

Details remain scant in the immediate aftermath, but Zelenskyy said on Monday that around 400 civilians had taken refuge at the Mariupol art school when it was hit.

There was no immediate word on the victims of the attack, which The Associated Press could not independently verify.

“They’re under the rubble, and we don’t know how many of them survived,” Zelenskyy said in a video address early Monday. “But we know we will definitely shoot down the pilot who dropped that bomb, like about 100 other mass murderers we’ve already shot down.”

The strike follows a series of attacks on civilian shelters, after Russian forces also shelled a theater in Mariupol on Wednesday where civilians took refuge. Authorities said 130 people had been rescued from the Donetsk Regional Academic Drama Theater but many more could remain under the rubble.

What was Russia’s offer to Mariupol?

Russian forces demanded that Ukrainian troops defending the strategic port lay down their arms and in return would be guaranteed a safe exit from the city via humanitarian corridors.

Colonel General Mikhail Mizintsev said Russia will wait until 5 a.m. Monday for a written response from Kyiv to the proposal, but did not specify what action Russia will take if its “humanitarian offer” is rejected.

Leaders including Ukrainian Deputy Prime Minister Iryna Vereshchuk and Mariupol Mayor Pyotr Andryushchenko quickly dismissed the idea. Vereshchuk said in remarks carried by news outlet Ukrainska Pravda that Kyiv had already told Russia that “there can be no discussion about surrender and laying down arms.”

Previous attempts to allow residents to evacuate Mariupol and other Ukrainian towns have failed or been only partially successful, with shelling continuing as civilians sought to flee.

What is happening in other cities in Ukraine?

In the Black Sea port of Mykolaiv, a Russian missile strike on a naval barracks killed at least 40 Ukrainian soldiers on Friday, Mayor Oleksandr Senkevich said in televised remarks. The missiles were fired from nearby Kherson region, he said.

Authorities in the eastern city of Kharkiv said at least five civilians were killed in the latest Russian bombardment, among the casualties including a nine-year-old boy. Kharkiv has been under siege since the start of the Russian invasion and faces relentless Russian artillery.

Some 70 orphaned babies have been evacuated from Sumy, another besieged Ukrainian city, in the northeast. The region’s governor said most infants require constant medical care and will be taken to an unspecified foreign country.

In Kyiv, at least 20 infants carried by Ukrainian surrogate mothers were stuck in a makeshift bomb shelter, waiting for their parents to enter the war zone to pick them up. They are cared for by nurses trapped in the shelter by constant shelling from Russian troops.

Zelenskyy said 7,295 Ukrainians were evacuated from combat zones on Sunday, including nearly 4,000 from Mariupol.

What did Pope Francis say?

In some of his strongest words since invading Russia on February 24, Francis told thousands in St. Peter’s Square on Sunday that every day brings more atrocities in what is a “senseless massacre “.

“There is no justification for this,” Francis said, in an apparent reference to Russia, which sought to justify its invasion as vital for its own defense. But Francis again stopped short of naming Russia as the aggressor. Pontiffs have generally decried wars and their devastating impact on civilians without citing warmongers by name.

“I feel great pain for those who don’t even have the chance to escape,” the pope added.

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Are there any new military developments?

The Russian military announced on Sunday that it had carried out a new series of strikes against Ukrainian military installations with long-range hypersonic and cruise missiles, a day after announcing that it had used its latest hypersonic missile for the first times in battle.

Russian Defense Ministry spokesman Major General Igor Konashenkov said the hypersonic Kinzhal missile hit a Ukrainian fuel depot at Kostiantynivka near Mykolaiv. The strike marked the second day in a row that Russia has used the Kinzhal, a weapon capable of hitting targets 2,000 kilometers (1,250 miles) away at 10 times the speed of sound.

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How are the Ukrainian refugees doing?

At church services across Europe on Sundays, Ukrainians prayed for peace in their war-torn country. From Germany to Romania to Moldova, newly arrived refugees have mingled with longtime members of the 1.5 million strong European Ukrainian diaspora in places of worship.

Thousands of refugees from Ukraine waited in long queues in the Polish capital of Warsaw Saturday to receive local identity papers that will allow them to continue their lives.

Refugees began queuing outside the National Stadium in Warsaw overnight to obtain the coveted PESEL ID cards that will allow them to work, go to school and obtain medical care or social benefits for the next 18 months.

Poland has taken in more than 2 million refugees from Ukraine – the bulk of more than 3.38 million people who the UN says have fled since Russia invaded Ukraine on February 24. Hundreds of thousands have flocked to Hungary, Slovakia, Moldova and Romania.

How many civilians died in Ukraine?

It’s hard to say, with full figures on wartime casualties hard to confirm. Since the start of the war until Friday, the Office of the United Nations High Commissioner for Human Rights (OHCHR) has recorded 2,246 civilian casualties in the country, including 847 killed and 1,399 injured.

Ukrainian officials say thousands of civilians have been killed.

Ukraine’s prosecutor general’s office reported on Saturday that 112 children have been killed since the fighting began. More than 140 children were injured.