<p><br /> Pope Benedict has led Christmas celebrations by holding mass at the Vatican.<br /> </p><p><br /> The Pontiff used the service to pray for peace, but is was marked by heightened security in Rome following parcel bomb attacks at two embassies in the capital.<br /> </p><p><br /> In front of some 10,000 people in St Peter's Basilica, Benedict said: "At this hour, full of thankfulness, we join in the singing of all the centuries, singing that unites heaven and earth, angels and men."<br /> </p><p><br /> Celebrating his sixth Christmas as pope, the 83-year-old Benedict earlier lit a candle at his window overlooking St Peter's Square for the official opening of the Vatican's nativity scene but a torrential downpour kept attendance low.<br /> </p><p><br /> Police were on heightened security in the Vatican and in Rome a day after parcel bombs injured two people at the Swiss and Chilean embassies in Rome. Anarchists claimed responsibility for the attacks, which injured one person at each embassy.<br /> </p><p><br /> Vatican guards were also more vigilant following security breaches for two consecutive years at Christmas Eve Masses by the same woman, Susanna Maiolo.<br /> </p><p><br /> Last year the woman, who has had a history of mental problems, jumped over a barricade as the pope walked up the basilica's main aisle and managed to pull him to the floor. The year before, she was stopped before she could reach him.<br /> </p><p><br /> Large televisions screen were placed outside in St Peter's Square but the rain kept many people away.<br /> </p>
