Pope Francis has inaugurated his papacy at a Mass in Rome, calling on global leaders and all the people of the world to defend the poor and the weak, reports the BBC.
Up to 200,000 people attended the Mass in St Peter's Square.
His homily focused on protection - of the environment, children, the elderly and those in need, who he said were "often the last we think about".
Pope Francis, formerly Argentine Cardinal Jorge Mario Bergoglio and now the first pontiff from the Americas, has since his election called for a "Church for the poor" and has struck an informal and spontaneous tone.
His chosen name, Francis, honours St Francis of Assisi, the 13th-Century son of an aristocrat who spurned a life of luxury to live with and for the poor.
Pope Francis' homily at the Mass began by focusing on Joseph and his role as protector - of Mary, Jesus and the Church.
Francis, 76, expanded the image, referring to Francis of Assisi and saying that the role of protector was not just a Christian one.He said: "It means protecting all creation, the beauty of the created world... It means respecting each of God's creatures and respecting the environment in which we live."
It means protecting people, showing loving concern for each and every person, especially children, the elderly, those in need, who are often the last we think about."
Francis called on "all those who have positions of responsibility in economic, political and social life" to be protectors of creation.
"To protect creation, to protect every man and every woman, to look upon them with tenderness and love, is to open up a horizon of hope," Francis said.
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