Pope Benedict XVI is to resign

Pope Benedict XVI is to resign at the end of this month after nearly eight years as the head of the Catholic Church, saying he is too old to continue at the age of 85.

The unexpected development - the first papal resignation in nearly 600 years - surprised governments, Vatican-watchers and even the his closest aides.

The then Cardinal Joseph Ratzinger became Pope after John Paul II's death.

The Vatican says it expects a new Pope to be elected before Easter.

The BBC's Alan Johnston in Rome says the news has come "out of the blue", and that there was no speculation whatsoever about the move in recent days.

Italian Prime Minister Mario Monti is quoted as saying he was "greatly shaken by this unexpected news".

A Vatican spokesman, Father Federico Lombardi, said that even the Pope's closest aides did not know what he was planning to do and were left "incredulous". He added that the decision showed "great courage" and "determination".

The brother of the German-born Pope said the pontiff had been advised by his doctor not to take any more transatlantic trips and had been considering stepping down for months.

Talking from his home in Regensburg in Germany, Georg Ratzinger said his brother was having increasing difficulty walking and that his resignation was part of a "natural process".

He added: "His age is weighing on him. At this age my brother wants more rest."