Security was tight at St Peter's Basilica in Rome on Christmas Eve when Pope Benedict delivered his traditional homily.
Last year at the same Mass a woman jumped the barriers and lunged at the Pope. The Vatican reviewed its security procedures after that, because the same woman had also tried to throw herself at the Pope a year earlier.
Security concerns had also been heightened by parcel bomb attacks on Thursday at two embassies in the Italian capital that injured two people.
The BBC's correspondent says plain-clothed security men followed the Pope watching for any sign of trouble as he walked in procession up the central nave of the basilica.
The 83-year-old pontiff stopped twice to bless babies held up to him.
Delivering his homily the Pope prayed for God to "implant his peace in our hearts" but also to "break the rods of the oppressors".
About 10,000 people attended the Mass.
Earlier, in heavy rain, Benedict lit a candle in his window, which overlooks St Peter's Square, to open officially the Vatican's nativity scene.
Thousands converge on Bethlehem
Thousands of people have also converged on the West Bank town of Bethlehem ahead of the midnight Mass at the Church of the Nativity - built at the site where Christians believe Jesus was born.
About 90,000 visitors are expected in the town during the Christmas season - up from about 70,000 last year, according to Israeli government figures.