On what is supposed to be Christianity's most joyful day, Pope Francis made an anguished Easter Sunday plea for peace in the "senseless" war in Ukraine and in other armed conflicts raging in the world, and cited the "troubling" risk of nuclear warfare."May there be peace for war-torn Ukraine, so sorely tried by the violence and destruction of this cruel and senseless war into which it was dragged," Francis said, speaking from the central balcony of St. Peter's Square.The pontiff had just finished celebrating Easter Mass in the square packed by faithful for the holiday for the first time since the pandemic began in early 2020. Applause erupted from many of the 50,000 people in the square and on a nearby avenue when he mentioned Ukraine."Please, please, let us not get used to war,'' Francis pleaded, after denouncing "the flexing of muscles while people are suffering." Yet again, the pontiff decried the war in Ukraine without citing Russian President Vladimir Putin for the decision to launch the invasion and attack against Ukraine on Feb. 24."Let us all commit ourselves to imploring peace, from our balconies and in our streets,'' Francis said. "May the leaders of nations hear people's plea for peace."In a clear reference to the threat of nuclear warfare, Francis quoted from a declaration by scientists in 1955: "'Shall we put an end to the human race, or shall mankind renounce war?'"Francis also drew attention to other wars in the speech known by its Latin name "Urbi et Orbi" -- to the city and to the world."May the conflict in Europe also make us more concerned about other situations of conflict, suffering and sorrow, situations that affect all too many areas of our world, situations that we cannot overlook and do not want to forget,'' Francis said.Among the conflicts cited by the pope were those in the Middle East. He exhorted peace and reconciliation for the peoples of Lebanon, Syria and Iraq.He also cited Libya as well as Yemen, "which suffers from a conflict forgotten by all."Earlier, the pontiff, who has a knee ligament problem, limped badly as he made his way to an altar set up in front of St. Peter's Basilica. The altar was shaded by a canopy against brilliant sunshine.Right after the end of Mass, Francis shook hands with prelates, then got aboard the white popemobile for a whirl through the square to greet cheering well-wishers among the rank-and-file faithful. He waved and patted the head of a baby who was handed to him. His smiles while greeting the crowd were a rare departure of late for the pope, who has used many of his appearances in recent weeks to issue somber denunciations of the war in Ukraine.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."Noting that in the Eastern Orthodox church 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.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.In Spain, believers and secular enthusiasts flocked back in large numbers to Holy Week processions this week for the first time since the start of the pandemic after most health restrictions were lifted.___Jill Lawless in London and Joseph Wilson in Barcelona contributed.