Pope Francis celebrated Easter Sunday Mass in St. Peter’s Square for the first time since the coronavirus pandemic, marking Christianity’s most joyous day at a time when the war in Ukraine has weighed heavily on his heart.

The pontiff, who has a knee ligament problem, limped badly as he stepped out from the back of St. Peter’s Basilica to reach an altar set up on the steps outside, shaded by a canopy against brilliant sunshine.

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Tens of thousands of people, numbered at 50,000 by the Vatican, many in shirtsleeves, packed the flower-bedecked square and a nearby boulevard to hear his words.

After the Mass, Francis, who is 85 and also suffers from chronic back problems, was set to move to the central balcony of the basilica, where he will deliver a geopolitical speech known in Latin as "Urbi et Orbi" (to the city and to the world), which pontiffs in recent decades have used to decry conflicts and injustices across the globe.

Pope Francis

Pope Francis holds a Paschal candle as he presides over a Easter vigil ceremony in St. Peter's Basilica at the Vatican, Saturday, April 16, 2022. (AP Photo/Alessandra Tarantino)

Right after the end of Mass, Francis shook hands with prelates, then boarded the white popemobile for a whirl through the square to greet cheering well-wishers.

Meanwhile, in London, Archbishop of Canterbury Justin Welby called for Russia to declare a cease-fire and withdraw from Ukraine. The leader of the Anglican church said Easter is a time for peace and not "blood and iron."

The Easter vigil ceremony in St. Peter's Basilica at the Vatican, Saturday, April 16, 2022.

The Easter vigil ceremony in St. Peter's Basilica at the Vatican, Saturday, April 16, 2022. (AP Photo/Alessandra Tarantino)

Noting that in the Eastern Orthodox church, which is followed by many in Russia and Ukraine, Sunday marks the start of Holy Week – with Easter coming on April 24 – Welby exhorted Russia to withdraw from Ukraine and commit to talks.

In an unusually blunt political remark, Welby also condemned the British government’s recent plan to send some asylum-seekers to Rwanda as going against God.

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Warm weather and the easing of many pandemic restrictions – including what had been for most of the pandemic in Italy a mandatory outdoor mask requirement – have seen tourism boom in Rome, with many visitors flooding the city for Holy Week ceremonies that culminated on Easter.

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In Spain, believers and secular enthusiasts flocked back in large numbers to Holy Week processions for the first time since the start of the pandemic after most health restrictions were lifted.