Thousands queue to pay their respects to former pope Benedict XVI

Thousands of Catholics began paying their respects on Monday to former pope Benedict XVI at St Peter's Basilica at the Vatican in Rome, at the start of three days of lying-in-state before his funeral.

The late Pope Emeritus Benedict XVI lying in state in the chapel of the 'Mater Ecclesiae' monastery in Rome. AP - Vatican Media

The queue began to form before dawn in the square in front of the basilica, the headquarters of global Catholicism, where Benedict's body was transferred earlier from the monastery in the Vatican grounds where he died Saturday aged 95.

Benedict led the Catholic Church for eight years before becoming the first pope in six centuries to step down in 2013, citing his declining mental and physical health.

His successor Pope Francis will lead the funeral on Thursday in St Peter's Square before Benedict's remains are laid to rest in the tombs beneath the basilica.

The Vatican on Sunday released photos of his corpse, dressed in red papal mourning robes and wearing a gold-edged mitre on his head, lying in state in the monastery chapel.

Members of the public will be able to pay their respects at St Peter's Basilica from 9:00 am on Monday and then on Tuesday and Wednesday.

A solemn but simple ceremony

Benedict's funeral will be "solemn but simple", the Vatican has said.

The Vatican has yet to release details of the guest list, beyond saying that it will include delegations from Italy and Benedict's native Germany.

The last papal funeral, of John Paul II in 2005, drew a million faithful and heads of state from around the world.

A brilliant theologian, Benedict alienated many Catholics with his staunch defence of traditional values. He struggled to impose his authority on the church as it battled a string of crises, most notably that centred on clerical sex abuse.

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Pope Francis paid tribute to Benedict in three New Year's events at the Vatican over the weekend, "thanking God for the gift of this faithful servant of the Gospel and of the Church".

Francis, who is 86 years old, has raised the prospect that he might follow Benedict's example and step down if he became unable to carry out his duties.

Last month, Francis revealed that he had signed a resignation letter to become effective should poor health prevent him from carrying out his duties.