Pope Benedict has led Christmas celebrations by holding mass at the Vatican.

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.

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."

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.

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.

Vatican guards were also more vigilant following security breaches for two consecutive years at Christmas Eve Masses by the same woman, Susanna Maiolo.

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.

Large televisions screen were placed outside in St Peter's Square but the rain kept many people away.