Roman Catholic cardinals left their Rome residences on Tuesday for the Vatican where they are to elect a new pope to tackle the daunting problems facing the 1.2-billion member Church.
The secret conclave, steeped in ritual and prayer, could carry on for several days, with no clear favourite in sight to take over the reins from Pope Benedict, who abdicated last month saying he was not strong enough to confront the Church's woes.
In a process dating back to medieval times, 115 "Princes of the Church" from 48 countries will shut themselves in the Vatican's frescoed Sistine Chapel on Tuesday afternoon after a public Mass in St. Peter's Basilica in the morning.
They will emerge from their seclusion only when they have chosen the 266th pontiff in the 2,000-year-history of the Church, which is beset by sex abuse scandals, bureaucratic infighting, financial difficulties and the rise of secularism.
The average length of the last nine conclaves was just over three days and none went on for more than five days.
Vatican-insiders say Italy's Angelo Scola and Brazil's Odilo Scherer have emerged as the men to beat. The former would bring the papacy back to Italy for the first time in 35 years, while the latter would be the first non-European pope in 1,300 years.
However, a host of other candidates from numerous nations also have been mentioned, including U.S. cardinals Timothy Dolan and Sean O'Malley, Canada's Marc Ouellet and Argentina's Leonardo Sandri.
Presented by Adam Justice