VATICAN CITY - A woman jumped the barriers in St. Peter's Basilica and knocked down Pope Benedict XVI as he walked down the main aisle to begin Christmas Eve Mass yesterday.

The 82-year-old pontiff quickly got up and was unhurt, said a Vatican spokesman, the Rev. Ciro Benedettini.

Benedict made no reference to the incident as the service started. As a choir sang, he sprinkled incense on the altar before opening the Mass with the traditional wish for peace in Latin: "Pax vobis" ("Peace be with you"). The faithful responded: "Et cum spiritu tuo" ("And also with you").

In his homily, delivered unflappably after the incident, Benedict urged the world to "wake up" from selfishness and petty affairs and find time for God and spiritual matters.

Footage aired on Italy's RAI state TV showed a woman dressed in a red, hooded sweatshirt vaulting over the wooden barriers and rushing toward the pope before being swarmed by bodyguards.

Video shot by a witness showed the woman grabbing the pope's vestments as she was taken down, with Benedict seemingly falling on top of her.

Benedict lost his miter and his staff in the fall. He remained on the ground for a few seconds before being helped back up by attendants. At that point, a few shouts of "viva il papa!" (long live the pope!) rang out, followed by cheers from the faithful, witnesses said.

The commotion occurred as the papal procession was making its way toward the main altar, and gasps rang out among people who packed the basilica. The procession came to a halt and security rushed to the trouble spot.

Benedettini said the woman who pushed the pope appeared to be mentally unstable and was arrested by Vatican police. Also knocked down was Cardinal Roger Etchegaray, 87. He broke a leg and was hospitalized.

After the incident, Benedict, flanked by tense bodyguards, resumed his walk to the basilica's main altar to start the Mass.

It was the second year in a row there was a security breach at the service. At the end of last year's Mass, a woman who had jumped the barriers got close to the pope but was quickly brought to the ground by security.

Benedettini said it was not immediately known if the same woman was involved in yesterday's intrusion.

Benedict's next scheduled public appearance is at noon today, when he is to deliver his traditional "Urbi et Orbi" speech (Latin for "To the city and the world") from the basilica's balcony.