Pope Benedict XVI received an ecstatic welcome from cheering crowds on Wednesday as he entered the Vatican's main audience hall for his second-to-last public appearance before stepping down on February 28.

After a lengthy standing ovation the 85-year-old told followers he was aware of the gravity of his decision to resign, but also of his diminishing physical and spiritual strength.

"I did this in full liberty for the good of the Church, after praying for long and examining my conscience before God, fully aware of the gravity of such an act," he said.

"Thank you for the love and prayer with which you have accompanied me ... Keep praying for me, for the Church and for the future pope," the pontiff added.

Around 12,000 people were gathered in the packed Paul VI auditorium to hear the pope hold his weekly audience address. He was frequently interrupted by applause and chants of "Benedeto," his name in Italian. Several members of the crowd held a prominent banner which read, "Thank You, Holiness."

Pope Benedict XVI will later celebrate Ash Wednesday, the official start of the Catholic Church's Lenten season. The service, usually held in a church on Rome's Aventine hill, was moved to St. Peter's Basilica to accommodate thousands expected to gather to pay their respect to the outgoing pontiff.

Suprise decision

Pope Benedict announced his decision to step down on Monday in a shock move which was believed to have taken the Vatican by surprise.

The German-born pope cited his advancing age and declining strength as reasons for his resignation, the first the Vatican has seen in around 600 years. The last pope to relinquish the papacy was Gregory XII in 1415.

Speculation is now rife over possible successors. Vatican spokesman Federico Lombardi has said that a new Pope is expected to be in place by Easter, which this year falls on March 31. No date has yet been set for the secret conclave to elect a new leader.

ccp/hc (AFP, AP)