VATICAN CITY: Pope Benedict XVI looked in good form on Friday as he delivered his traditional Christmas message, urging tolerance for migrants, a day after falling during an assault at St Peter's Basilica.

"In the face of the exodus of all those who migrate from their homelands and are driven away by hunger, intolerance or environmental degradation," the Roman Catholic Church calls for "an attitude of acceptance and welcome," the pope said.

The 82-year-old pontiff appeared upbeat and calm as he gave the "urbi et orbi" (to the city and the world) address to tens of thousands of pilgrims gathered in St Peter's Square and millions around the world.

The spiritual leader of the world's 1.1 billion Roman Catholics then gave blessings in 65 languages from Maltese to Mongolian.

In the assault on Thursday, a 25-year-old woman leapt over a security barrier and managed to knock down the pope in a dramatic start to his celebration of Christmas Eve mass.

Masses of pilgrims gasped as a security guard failed to stop her from grabbing Pope Benedict's vestments near the neck and pulling him to the floor as several other people fell over in the melee.

Relieved applause broke out as the pontiff got back on his feet within moments.

Pope Benedict went on to celebrate the mass undaunted by the assault, speaking out in his homily against selfishness as Christians across the world celebrated the birth of Jesus Christ.

Meanwhile the Vatican identified the pontiff's assailant as Susanna Maiolo, 25, and said she was hospitalised for "necessary treatment."

Vatican spokesman Federico Lombardi told AFP that Maiolo, of dual Swiss and Italian nationality, as "apparently unbalanced."

She tried to get near the pope on the same occasion last year but security guards held her back, the spokesman said.

Prominent French Cardinal Roger Etchegaray, 87, broke a leg in the incident though he was several metres (yards) away.

He will undergo surgery for a fracture to the neck of a thighbone, the Vatican said.

Lombardi played down Thursday's incident, praising Pope Benedict's "great self-control and control of the situation."

He added: "It was an assault, but it wasn't dangerous because she wasn't armed."

The Christmas Eve mass is one of few occasions when tourists and pilgrims can get close to the pontiff.

Papal security has been tightened since Mehmet Ali Agca, a Turk, shot and nearly killed Benedict's predecessor John Paul II in St Peter's Square in May 1981.

Thursday's incident occurred less than two weeks after a man with a history of mental problems attacked Italian Prime Minister Silvio Berlusconi after a political rally in Milan, breaking his nose and inflicting other facial injuries.

The attack on the pope took place amid concern over his health after a Vatican decision to schedule the mass two hours earlier than the traditional midnight hour due to the pontiff's advanced age.

Lombardi insisted that the change, a Vatican first, was only a "sensible precaution" for the octogenarian pontiff, adding that it was "no cause for alarm."

Lombardi said the move was aimed at making Christmas "a little less tiring for the pope, who has many engagements during this time".

Benedict has had no notable health problems since his 2005 election apart from a fractured wrist from a fall in July while holidaying in northern Italy.

Four years before he became pope, however, then Cardinal Joseph Ratzinger spent nearly a month in hospital following a brain haemorrhage, according to the German daily Bild. It said he has suffered from fainting spells.

John Paul II insisted on observing the tradition of beginning the mass at midnight despite years of ill health, notably the ravages of Parkinson's disease, at the end of his life.