Pope Benedict XVI delivered an emotional final Sunday prayer in St Peter's Square, saying God had told him to devote himself to quiet contemplation but pledging not to "abandon" the Church.
Tens of thousands of supporters turned out for Benedict's weekly Angelus prayer, his last ahead of his formal resignation on Thursday, often interrupting him with clapping, cheering and chanting.
"The Lord is calling me to climb the mountain, to dedicate myself even more to prayer and meditation. But this does not mean abandoning the Church," the pope said from the window of his residence in the Vatican, his voice breaking with emotion.
"If God is asking me to do this it is precisely so I can continue to serve with the same dedication and love as before but in a way that is more appropriate for my age and for my strength."
The pope thanked the crowd with a final unscripted call, telling them: "We will always be close!"
The 85-year-old leader of the world's 1.2 billion Catholics said earlier this month he will be stepping down because he lacks the strength to carry on in an announcement that shocked the world.
He is the first pope since the Middle Ages to resign.
The final days of his pontificate however are being overshadowed by scandal over two cardinals -- one accused of covering up paedophile abusers and the other accused of "inappropriate acts" -- who are set to take part in the conclave to elect his successor.
That did not deter an estimated 100,000 people from coming out to bid the pope a final farewell on Sunday -- many times more than usually attend the traditional event in St Peter's Square.
"Holy Father, We Love You" read one banner, while others said: "Thank You, Your Holiness" and "Dear Father, We'll Miss You".
"I have come to support the pope and to ask for his blessing," said Joao-Paulo, a 26-year-old seminarian from Brazil.
Birgit Marschall, 37, a teacher from Germany, said: "He is an intellectual who speaks in simple language, who writes what we have in our hearts."
Claire Therese Heyne, a 34-year-old theology student from the United States, said the pope "must have had a very strong reason" to leave.
"It is an act of courage and humility," she said.
Benedict will be only the second pope to resign of his own free will in the Church's 2,000-year history.
But Gianpaolo, 33, said Benedict had been "less courageous" than his predecessors, and stressed the need for major reforms.
"The Church has to have a major reflection after this resignation. Something has changed inside the Church and this decision reflects this," said Gianpaolo, who came with his two sons.
-- 'Completely false news stories' --
Forty-five-year-old Linda from Wales said: "He was not so open as the last popes before him. A new pope should be more open to people, to new ideas."
There was tight security in and around the Vatican, with more than 100 police officers and snipers on surrounding rooftops, as well as two field clinics and hundreds of volunteers to help pilgrims.
The event was being seen as preparation for the pope's final general audience in St Peter's on Wednesday where around 200,000 people are expected.
Following his resignation announcement, some Italian media have said that Benedict's health may be worse than has been revealed, and others have said an explosive report on intrigue, corruption and blackmail in the Vatican was to blame.
The Vatican's Secretariat of State -- the government of the Catholic Church -- took the unusual step on Saturday of issuing a statement condemning "completely false news stories" as an attempt to influence the vote of cardinals.
The upcoming conclave is also under a cloud over allegations that one of the 117 "cardinal electors" -- US clergyman Roger Mahony -- had covered up for paedophile priests for years in Los Angeles.
Another cardinal, Britain's Keith O'Brien, has been reported to the Vatican over claims of inappropriate behaviour by four people, the Observer newspaper reported on Sunday.
The Vatican said the pope was considering the case.
John Allen, a Vatican expert at the National Catholic Reporter, said current discussions on sexual abuse by priests showed "how enormously damning this scandal has been for the Church."
"Even at the most awesome moment in the life of the Church, even then, this scandal rears its ugly head," he said, referring to the papal conclave.
The Vatican has said Benedict will retire to the papal summer residence of Castel Gandolfo near Rome for the next two or three months while a former monastery inside the Vatican is renovated for his use.
Vatican sources said he is likely to retain the title of "His Holiness" -- an unprecedented move -- and will also be known under the previously unheard-of title of "Bishop Emeritus of Rome".
In Catholic theology the pope, as the successor of Saint Peter, is the bishop of Rome.