A Russian ultimatum for the last remaining Ukrainian forces in Mariupol to surrender expired on Sunday, with Moscow poised for a major strategic victory in the southeastern port city.

In Kyiv, renewed Russian airstrikes hit an armaments factory, despite Moscow shifting its military focus to gaining control of the eastern Donbass region and forging a land corridor to already-annexed Crimea.

"During the night, high-precision, air-launched missiles destroyed an ammunitions factory near the settlement of Brovary, Kyiv region," Russia's Defense Ministry said, the third such airstrike near the capital in as many days.

Ukrainian Deputy Prime Minister Iryna Vereshchuk urged Russian forces to allow evacuations from Mariupol, which Moscow's forces claim to have brought under their control, though Ukrainian fighters remain holed up in the city's fortress-like steelworks.

Moscow on Saturday issued an ultimatum to the fighters, urging them to lay down their arms by 6 a.m. Moscow time (3 a.m. GMT) and to evacuate before 1 p.m.

"Once again, we demand the opening of a humanitarian corridor for the evacuation of civilians, especially women and children, from Mariupol," Vereshchuk wrote.

Russia's Defense Ministry said that there were up to 400 mercenaries inside the encircled Azovstal steel plant, calling on Ukrainian forces inside to "lay down their arms and surrender in order to save their lives."

Moscow claims Kyiv has ordered fighters of the nationalist Azov battalion to "shoot on the spot" anyone wanting to surrender.

Ukraine President Volodymyr Zelenskyy said that if Russian forces kill Kyiv's troops remaining to defend the city, then a fledgling negotiation process to end nearly two months of fighting would be ended.

'Inhuman'

Zelenskyy said the situation in Mariupol is "inhuman" and called on the West to immediately provide heavy weapons.

Mariupol has become a symbol of Ukraine's unexpectedly fierce resistance since Russian troops invaded the former Soviet state on Feb. 24.

"The situation in Mariupol remains as severe as possible. Just inhuman," Zelenskyy said in a video address.

"Russia is deliberately trying to destroy everyone who is there."

The U.N. World Food Programme has said that over 100,000 civilians in Mariupol are on the verge of famine and lacking water and heating.

Ukraine's Minister of Digital Transformation Mykhailo Fedorov said the city was on "the verge of a humanitarian catastrophe" and warned the country was compiling evidence of alleged Russian atrocities there.

"We will hand everything over to The Hague. There will be no impunity," he said.

With fighting raging in the east, Vereshchuk said that humanitarian corridors allowing civilians to flee would not open on Sunday after failing to agree to terms with Russian forces.

Ukrainian authorities have urged people in the eastern Donbass area to move west to escape a large-scale Russian offensive to capture its composite regions, Donetsk and Luhansk.

'Easter of war'

Celebrating Easter Sunday in Rome, Pope Francis called for peace in Ukraine during this "Easter of war."

"May there be peace for war-torn Ukraine, so sorely tried by the violence and destruction of the cruel and senseless war into which it was dragged," the pontiff said in his traditional Urbi et Orbi address on St. Peter's Square at the Vatican.

"Let there be a decision for peace. May there be an end to the flexing of muscles while people are suffering."

Francis said he held "in my heart all the many Ukrainian victims, the millions of refugees and internally displaced persons, the divided families, the elderly left to themselves, the lives broken and the cities razed to the ground.

"I see the faces of the orphaned children fleeing from the war."

A week ahead of Orthodox Easter, men, women and children of all ages streamed into the Bernardine Monastery in the western city of Lviv to bless sprigs of pussy willow on Orthodox Palm Sunday.

Under an ornate gilded ceiling, worshippers huddled on pews or found standing space near the door to engage in private prayer.

On the square outside, Natalia Borysiuk, a 29-year-old who works in the IT sector, held a posy of pussy willow and wheat bound in blue and yellow ribbon, the colors of the Ukrainian flag. She said she had come to pray for "peace and victory."

"I can't even talk about how in these eastern cities of Ukraine and Kyiv they suffer now. It's terrible. But here we can just go to church and pray, and believe in our beautiful and peaceful future," she said.

'Unpredictable consequences'

Russia warned the United States this week of "unpredictable consequences" if it sends its "most sensitive" weapons systems to Ukraine, as Zelenskyy has requested.

Its Defense Ministry claimed Saturday to have shot down a Ukrainian transport plane in the Odessa region, carrying weapons supplied by Western nations.