Roman Catholics and well as other Christian churches will all be monitoring the next Vatican conclave which will likely be by the end of March. The conclave is the Catholic Church's selection for the next pope.

Vatican spokesman Father Federico Lombardi made the announcement on Monday right after Pope Benedict XVI said he would resign from his office for health reasons. Benedict, the 265th pope in the Catholic Church's history, reigned for eight years.

Born Joseph Alois Ratzinger in Bavaria, Germany, he became head of the Roman Catholic Church in April 19, 2005. He is 85 and the first pope to quit his office in almost six centuries, the last being Pope Gregory XII who stepped down in 1415 to end the Great Western Schism.

Various church and national leaders as well as ordinary Catholics were shocked by the Pope's decision, announced at a meeting of cardinals on Monday morning.

Angelo Sodano, a senior Vatican cardinal, described the papal announcement as a bolt from the blue. Italian Prime Minister Mario Monti told BBC he was shaken by the news, while Steffen Seibert, spokesman of the German government said, "He has left a very personal signature as a thinker as the head of the Church, and also as a shepherd. Whatever the reasons for his decision, they must be respected."

Pope Benedict will not participate in the March conclave, Fr Lombardi said. After Feb 28, he will move to Castelgandolfo, the pope's summer residence near Rome and eventually transfer to a former monastery within Vatican territory.

Church observers said there is no clear front-runner who will succeed Pope Benedict, although during his election in 2005, he was considered one of the frontrunners by virtue of his position then as the head of the Congregation for the Doctrine of the Faith.

As early as January 2005, he was identified by Time Magazine as a top contender for the papal position. However, his election was considered a surprise since the frontrunners are traditionally passed over by the conclave.

There are 209 cardinals, but only 118 are under 80 years old with the right to vote for the next pope.

National Post, citing the Irish betting site Paddy Power, named Ghanian Cardinal Peter Turkson as the 9-4 favourite to be the next pope, followed by Canadian Cardinal Marc Ouellet 5-2 and Nigerian Cardinal Francis Arinze 3-1.

Cardinal Turkson was appointed in 2009 as the president of the Pontifical Council for Justice and Peace.

While the pope's resignation shocked the Catholic world, some media church officials had actually anticipated the move as early as two years ago.

While with his move, Pope Benedict will be controversial, especially with more sex scandals involving clergy coming out during his term, although he is not in Time Magazine's list of the 10 most controversial popes, namely:

1. Stephen VI - Hated his predecessor, Pope Formosus, so much that he had the rotting 9-month old corpse dug up, redressed in papal vestments and seated on the throne to be tried.

2. Urban VI - Because of his harsh leadership style, 13 French cardinals fled Rome who declared within months his election as null because it was done in fear.

3. Alexander VI - Gave wealth and nepotism a bad name by buying his way to St. Peter's and appointing his family members to powerful positions

4. Pius XII - Criticised for not speaking against the atrocities of the Holocaust.

5. Benedict IX - Sold the papacy and was called by St Peter Damian as a "demon from hell in the disguise of a priest."

6. Boniface VIII - Sent mercenaries to destroy other people's castles, forfeited properties and parceled out the lands to his family.

7. Nicholas III - Gave land and political power to his family members, which earned him a place in Dante's eighth circle of Hell.

8. Clement V - Played countries one against the other, collected oppressive high taxes and gave land to supporters and family members.

9. Leo X - Drained the papal treasury within two years and had to sell off pieces of the Vatican palace.

10. Sergius III - Rumoured to have ordered the death of another pope and had an affair with the daughter of a powerful count.