Two "super-powerful bombs" rocked Mariupol on Tuesday as Ukrainian authorities made a fresh attempt at rescuing civilians from the besieged port city which has suffered relentless shelling since Russia's invasion began almost a month ago.
More than 200,000 people are trapped in the strategic city described by those who managed to escape as a "freezing hellscape riddled with dead bodies and destroyed buildings", Human Rights Watch said, quoting figures provided by a local official.
"We know that there will not be enough space for everyone" on Tuesday, but "we will try to carry out the evacuation until we have gotten all the inhabitants of Mariupol out," vowed Deputy Prime Minister Iryna Vereshchuk in a video address.
Two "super-powerful bombs" slammed into the city even as rescue efforts were ongoing, said Mariupol local authorities, without giving an immediate toll.
"It is clear that the occupiers are not interested in the city of Mariupol, they want to raze it to the ground, to reduce it to ashes," the authorities said.
Ukrainian leader Volodymyr Zelenskyy turned to Pope Francis for help, urging the pontiff to mediate in the conflict and to help end "human suffering".
Earlier, Zelenskyy said all issues would be on the table if Russia's Vladimir Putin agreed to direct talks to end the war, including the contested eastern regions Donbas and the annexed Crimea peninsula.
But he warned his country would be "destroyed" before it surrenders.
The Kremlin in return said it would like to see negotiations with Kyiv to be "more active and substantial".
Russia's position was "well-known to the Ukrainian side" because Moscow handed over its demands in written form "many days ago", Kremlin spokesman Dmitry Peskov said, adding, "we would like a more substantial and swift answer".
The two sides are currently holding negotiations remotely after several rounds of talks between delegations meeting on the border between Belarus and Ukraine, but little progress has been made.
With Russia's military campaign appearing to stall, fears are growing that Putin may resort to even more drastic means to turn the tide.
US President Joe Biden warned that Putin was considering using chemical and biological weapons in Ukraine, as he described Moscow's tactics as increasingly "brutal".
Biden is due to travel to Brussels on Thursday for a series of summits gathering NATO, EU and G7 leaders, before heading to Poland, which has received the bulk of more than 3.5 million Ukrainians fleeing war in their country.
Since Russia launched its invasion on February 24, at least 117 children have been killed in the war, Ukraine's federal prosecutor said.
Some 548 schools have been damaged, including 72 completely destroyed.
Russia has pushed on with its assaults, in the face of unprecedented Western sanctions that has led international companies to pull out of the country and left its key banks shut out of the SWIFT messaging system.
But both Western and Ukrainian experts believe the war was not going the way the Kremlin had planned.
The invading forces were running out of supplies, Pentagon spokesman John Kirby told CNN, describing them as "frustrated" and "stalled."
The assessment was corroborated by Ukraine's army command which said Russian troops now had ammunition, food and fuel to last just three days.
Three hundred Russian soldiers have defected in the north-eastern Sumy region, added the army command on Facebook.
Even in areas Russia has captured, resistance has persisted.
Ukrainians "are going after Russians and pushing them out of places where the Russians have been in the past," Kirby said, pointing to Mykolaiv, in the south.
"We have seen this now increase over the last few days."
In the occupied southern city of Kherson, Ukraine's leaders on Tuesday accused Russian troops of firing on unarmed protesters.
A series of videos posted on social media and the messaging app Telegram showed citizens gathering in Kherson's "Freedom Square" protesting against Russia's recent seizure of the city.
Russian soldiers could be seen firing into the air.
An elderly person was wounded, said Ukraine's foreign ministry in a statement.
"The humanitarian situation is rapidly deteriorating," it said, accusing Moscow of refusing to allow for an aid corridor to evacuate civilians and channel in food.
More critical was the plight of residents from Mariupol, who have been without electricity and water for days.
Several bids to evacuate the population had been made but they have rapidly collapsed with both sides trading blame over violations.
Getting civilians out was the priority on Tuesday, said Ukrainian officials. Three routes have been drawn up linking the port city to Zaporizhzhia, Deputy Prime Minister Vereshschuk said.
European Union foreign policy chief Josep Borrell had described as a "massive war crime" the siege of Mariupol, which had killed more than 2,000 people.
Russia had given Mariupol until Monday morning to surrender, but Kyiv rejected the ultimatum and said the city's resistance was bolstering the defence of all of Ukraine.
Mariupol is a pivotal target in Putin's war -- providing a land bridge between Russian forces in Crimea to the southwest and Russian-controlled territory to the north and east.
Meanwhile in Kyiv, a 35-hour curfew came into effect from 8:00 pm (1800 GMT) Monday, after Russian strikes laid waste to the "Retroville" shopping complex, killing at least eight people.
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Russia claimed the mall was being used to store rocket systems and ammunition.
Maxim Kostetskyi, 29, a lawyer, said residents in the capital were using the "pause" imposed by the lockdown to regroup.
"We don't know if the Russians will continue with their efforts to encircle the city, but we are much more confident, the morale is high and inspiring," he told AFP.
Making his relentless push on the diplomatic front, Zelenskyy has renewed a call for direct talks with Putin.
The Ukrainian president said he was even willing to discuss Russian-occupied Crimea and the breakaway Russian regions in Donbas, though he insisted he still believes they must be returned to Ukraine.
"At the first meeting with the president of Russia, I am ready to raise these issues," he said, adding that any agreement involving "historic" changes would be put to a national referendum.
For UN chief Antonio Guterres, it was high time for Russia to end its "absurd war" in Ukraine.
"Even if Mariupol falls, Ukraine cannot be conquered city by city, street by street, house by house," he said.
"This war is unwinnable. Sooner or later, it will have to move from the battlefield to the peace table. That is inevitable," he added.
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