Pope Benedict XVI Installed

The pope was solemnly bestowed the insignia of his high office -- a scarf-like woollen pallium hung around his neck and the Fisherman's Ring -- during the open-air mass, watched by millions on television.

On a joyous day for the Church's one billion Catholics, the new pope seized the moment in an ebullient homily in which he issued a rallying call for Christian unity and said that the "young" Church held within itself the future of the world.

"During those sad days of the pope's illness and death, it became wonderfully evident to us that the Church is alive. And the Church is young," he said, answered by a great welling of applause from the massive, flag-waving crowd.

"She holds within herself the future of the world and therefore shows each of us the way towards the future," said the pope.

Appeal for Christian unity

In his message, the pope appealed for the unity of Christian Churches, saying there should be "one flock, one shepherd."

In Benedict XVI's first public mass as pope, there were signs of a growing rapport with ordinary Catholics as pilgrims interrupted his homily more than 30 times with encouraging applause, particularly following his repeated requests to "pray for me" as he begins his pontificate.

"And now at this moment, weak servant of God that I am, I must assume this enormous task, which truly exceeds all human capacity. How can I do this. How will I be able to do it?" he asked, answered again by an encouraging ovation.

"I am not alone," the pope said. "And your prayers, my dear friends, your indulgence, you love, your faith, and your hope accompany me."

The 78-year-old pontiff, wearing a gold robe over sacred white vestments, emerged from St Peter's Basilica at the start of the mass in a procession of 150 cardinals as a choir chanted the Laudes Regiae, a litany invoking divine assistance for the new pontiff.

The huge crowd erupted into applause and a frenzy of flag-waving fervor when the new pope smiled and waved as he stood for a few moments before the doors of the basilica.

Shortly before, the new pontiff and Patriarchs of Eastern Catholic churches gathered around the tomb of St Peter, the apostle chosen by Jesus as the first leader of his church.

The world watches

With many world leaders attending the mass, Italy deployed an array of security measures including 10,000 security forces, and has closed airspace over Rome and the Vatican, protected by Hawk anti-missile systems and an AWACS surveillance plane.

Among the dignitaries were King Juan Carlos and Queen Sofia of Spain, the latter wearing a traditional white lace dress and mantilla.

President Horst Köhler and Chancellor Gerhard Schröder were attending from the pope's native Germany, as well as Italy's Prime Minister Silvio Berlusconi, Britain's Prince Philip and a host of other heads of state and government and ministers from 140 nations.

Continue to read about Benedict XVI's inaugural sermon.

Homage to John Paul II

The thronged square was bathed in spring sunshine and decorated with flowers, in stark contrast to the leaden skies and winds which buffeted the requiem mass for Pope Benedict's predecessor John Paul II just two weeks ago.

Pope Benedict peppered his homily with references to his predecessor, urging Christians at the outset of his pontificate: "Do not be afraid."

Recalling the late pontiff's words at his own 1978 inauguration, the new pope said that by trusting in God "we lose nothing, absolutely nothing, of what makes life free, beautiful and great."

Citing episodes in the Bible, he compared Christian unity to a net cast by the fisherman St Peter on Jesus' instructions which held fast despite bulging with fish.

"Alas, beloved Lord, with sorrow we must now acknowledge that it has been torn!" he said. "Let us do all we can to pursue the path toward the unity you have promised... Grant that we may be one flock and one shepherd.

"Do not allow your net to be torn, help us to be servants of unity."

Greeting Jewish people

Greeting representatives of other faiths, he extended a message to "the Jewish people, to whom we are joined by a great shared spiritual heritage, one rooted in God's irrevocable promises."

Pilgrims and members of religious communities had been making their way to the Vatican since before dawn.

"Lieber Papst, wir Kinder lieben Dich" (Dear pope, we children love you) read one of the thousands of banners displayed by pilgrims, this one prepared by Italian primary school students in the new pope's native tongue.

"He's very holy, he won't listen to any nonsense about gay marriage," said Sister Ruth Augustus, a Franciscan missionary from London, referring to a Spanish bill passed this week to authorize same-sex couples to marry and adopt children.

"And he wants to kick out the priests who have sex with children," said Augustus, carrying a statue of the Virgin Mary and baby Jesus.

At least two people fainted in the crowd, to be wheeled away by volunteers from Italy's civil protection organization.

Germans and the German flag were prominent in the crowd, including a group of 400 people from the Bavarian town of Traunstein dressed in the traditional skirts and lederhosen of their region.

"It is a great honor. It is the first pope from upper Bavaria," said Hans Wembacher.

Global audience

In a mass reflecting the worldwide reach of the Catholic Church, the scripture readings were in English and Spanish and prayers were offered in French, German, Chinese, Portuguese, Arabic, Greek and Latin.

The Vatican said the new pope would tour the square greeting pilgrims from an open-topped car in the manner made famous by his predecessor at the end of the mass.

But a spokesman said he would not walk into the crowd.

"We would stay until 4 p.m. in the afternoon," if he did.