Pope Benedict XVI led the Vatican's Christmas celebrations late Friday with the traditional midnight Mass, which began amid tightened security measures following last year's intrusion by a mentally disturbed woman, dpa reported.
Thousands of people flocked to St Peter's Basilica as Benedict began presiding over the ceremony. Many more followed the proceedings on giant video screens in St Peter's Square, on a mild but wet winter's night.
Benedict, wearing golden robes and his bishop's mitre, walked into the Basilica in procession with other clerics. The pontiff stopped occasionally, briefly greeting well-wishers, many of them holding camera phones.
During the same event in 2009, a Swiss-born woman, Susanna Maiolo, jumped over a barrier and lunged at the pontiff, knocking him down. Benedict was unhurt in the resulting fracas, but an elderly cardinal suffered a broken leg.
Maiolo had already tried to accost the pontiff during the 2008 Christmas Mass but was blocked by security guards.
As in 2009, Friday's midnight mass began at 10 pm (2100 GMT) instead of midnight - an earlier slot aimed to give the 83-year-old pontiff a few extra hours of sleep before his Christmas Day duties, the Vatican said.
In his mass homily, the leader of the world's more than 1 billion Catholics was expected to stress that Jesus' coming - the event that Christians celebrate at Christmas - gives mankind the hope that lasting peace will be achieved on Earth.
Earlier, the Vatican unveiled in St Peter's Square its Nativity scene, recreating the scene of Jesus' birth - a custom revived in 1982.
The story narrates how Jesus' mother, Mary, and her husband, Joseph, unable to find lodging, seek shelter in a stable and using a manger, or livestock feeding trough, as a crib for the infant.
This year, the traditional Nativity figures are complemented by a set of nine statues created by Filipino sculptor Kublai Ponce-Millan. These include musicians playing indigenous instruments and a family in a boat pulling a net, heavy with fish.
The statues are a gift from the Philippines government to mark next year's 60th anniversary of the establishment of diplomatic relations between the majority Catholic Asian nation and the Vatican.
The Nativity scene stands next to the Vatican's Christmas tree - this year a 34-metre-high Norwegian spruce from Italy's north-eastern Alpine region of Alto Adige.
Benedict has encouraged Catholics to display their own Nativity scenes and Christmas trees, both "spiritual" symbols representing Christ's appearance on Earth, according to the German-born pontiff.
On Saturday, Benedict was scheduled to deliver his Christmas Day blessings and traditional Urbi et Orbi message "to the city and to the world."