Pope Francis' inauguration ceremony has been underway in Rome. World leaders and religious dignitaries were among those attending.
An estimated 200,000 faithful attended the ceremony that lasted for two hours.
Delegations from 33 Christian Churches and 132 national governments or international organizations, as well as Jewish, Muslim and Buddhist leaders were attending.
German Chancellor Angela Merkel, US Vice President Joe Biden and Argentinian President Cristina Fernandez de Kirchner are among them. Zimbabwe's President Robert Mugabe is reported to have defied a European Union travel ban to be in the Vatican for the ceremony.
Special significance was seen in the attention of Ecumenical Patriarch Bartholomew from Istanbul. The first time the spiritual head of Orthodox Christians attended a Roman pope's inaugural Mass since the Great Schism between western and eastern Christianity in 1054.
During the ceremony, Francis received the pallium - a special scarf - and the fisherman's ring, both symbols of the papacy.
Confirming his relative taste for simplicity, the pope has opted for a gold plated silver ring, rather than one made of pure gold.
In line with this message he vowed to protect the weak and the poor.
The Church's mission "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," he said in the homily.
Before serving mass, Francis moved around St. Peter's Square to greet the faithful. Since his election six days ago he has repeatedly ignored protocol, going out of his way to reach out to his followers.
Tuesday's inauguration was televised and broadcast live around the world for the 1.2 billion followers of the Catholic Church.
The 76-year-old Argentine was elected the 266th leader of the Catholic Church on Wednesday last week, following the surprise resignation last month of Pope Emeritus Benedict XVI.
rg/dr (dpa, AFP, AP, Reuters) dw de
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