Pope Benedict made the surprise announcement during a meeting with Vatican cardinals on Monday.

Citing a lack of strength owing to his "advanced age," Benedict said he needed to resign because he could no longer carry out his duties.

"For this reason, and well aware of the seriousness of this act, with full freedom I declare that I renounce the ministry of Bishop of Rome, Successor of Saint Peter," he said according to a statement from the Vatican.

The announcement was made in Latin.

The Vatican's spokesman, Federico Lombardi, said the pontiff would serve until the end of the month.

"The pope announced that he will leave his ministry at 8 pm (1900 GMT) on February 28," he said.

By mid-March, the College of Cardinals is expected to be elect a successor.

The last pope to relinquish the papacy was Gregory XII in 1415.

Well-known long before pope

Pope Benedict was elected to the office on April 19, 2005, at the age of 78. Since then, the German native has been the subject of much international criticism for his conservative stance on Church issues, including that of whether to allow women to enter the priesthood and human sexuality.

By stepping down, Pope Benedict is setting an unusual precedent as the Bishop of Rome generally remains in the position until death. The last one to resign was Pope Gregory XII in 1415.

His predecessor, John Paul II - Polish-born Karol Jozef Wojtyla - led the Church for 27 years until his death at age 84.

Pope Benedict XVI was born in Marktl am Inn, Bavaria on April 16, 1927. Prior to his election as pope, he was a widely respected theologian. During the Second Vatican Council in the early 1960s, he provided expertise to Cardinal Joseph Frings of Cologne.

From 1977 to 1982, Ratzinger was the Cardinal of Munich. Pope John Paul II appointed him to prefect of the Congregation for the Doctrine of the Faith in 1981, in a role in which he became known as a staunch defender of Church doctrine.

kms/pfd (Reuters, AFP, AP, dpa)