Around 100 Ukrainian civilians were being evacuated from a ruined steelworks in the city of Mariupol on Sunday, Ukrainian President Volodymyr Zelensky said, after the United Nations had confirmed a “safe passage operation” was in progress there.

Mariupol, a strategic port city on the Azov Sea, has endured the most destructive siege of the war, with Pope Francis, in an implicit criticism of Russia, telling thousands of people in St Peter’s Square on Sunday it had been “barbarously bombarded”.

“Grateful to our team! Now they, together with (United Nations), are working on the evacuation of other civilians from the plant,” Zelensky tweeted. The evacuees would reach the Ukrainian-controlled city of Zaporizhzhia on Monday, he said.

With fighting stretching along a broad front in southern and eastern Ukraine, US House of Representatives Speaker Nancy Pelosi pledged continued US support for Ukraine when she met Zelensky in an unannounced visit to Kyiv.

Russia, meanwhile, said it had destroyed a stock of Western-supplied weapons at an airfield near Odesa, in southern Ukraine.

Moscow has turned its focus to Ukraine’s south and east after failing to capture Kyiv in the early weeks of a war that has flattened cities, killed thousands of civilians and forced more than 5 million to flee the country.

In Mariupol, Russia declared victory on April 21 even as hundreds of holdout Ukrainian troops and civilians took shelter in the city’s Azovstal steel works, a vast Soviet-era complex with a network of bunkers and tunnels.

Negotiations to evacuate the civilians had repeatedly broken down in recent weeks, with Russia and Ukraine blaming each other.

US support

Footage posted by Zelensky on Twitter on Sunday showed him, flanked by an armed escort and dressed in military fatigues, greeting a US Congressional delegation led by Pelosi outside his presidential office the previous day.

“Our delegation travelled to Kyiv to send an unmistakable and resounding message to the entire world: America stands firmly with Ukraine,” Pelosi, the highest ranking US official to visit Ukraine since Russia invaded on February 24, said in a statement.

Moscow calls its actions a “special military operation” to disarm Ukraine and rid it of anti-Russian nationalism fomented by the West. Ukraine and the West say Russia launched an unprovoked war of aggression.