Pope Benedict thanks public for 'love and prayers'
The Pope was cheered by crowds as he entered and began speaking at a weekly audience in a hall at the Vatican.
He said he resigned "for the good of the Church", aware of his own declining spiritual and physical strength.
Later he will hold what is expected to be his last public Mass, for Ash Wednesday, in St Peter's Basilica.
The 85-year-old will continue with his diary as usual until the day he officially retires at the end of February, Vatican officials say.
By the end of Lent, in six weeks' time, there is expected to be a new Pope.
The Pope held his weekly general audience at its traditional venue, the audience hall in the Vatican, Kazinform has learnt from BBC.
Thousands of people gathered in the hall to greet him, giving him a standing ovation as he arrived, and cheering as he began and finished speaking.
The BBC's David Willey in Rome says he looked tired and drawn.
Pope Benedict thanked them for their warm greeting and their sympathy.
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