Benedict XVI, a German theologian with a cult following among traditionalist Catholics, was a conservative intellectual who ended his troubled tenure with the most revolutionary act committed by a modern pope.

He died at 95 on Saturday at the monastery on Vatican grounds where he has lived in relative seclusion since resigning on February 28, 2013.

Benedict was the first pope in more than 600 years to take such action. That cleared the way for the election of his Argentinian successor Francis, the first non-European Catholic Church leader since the 8th century.

"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry," Benedict said in his resignation speech, speaking in Latin.

His decision ended an eight-year pontificate that started in 2005.

Large parts of it were spent dealing with scandals - first the fallout from worldwide allegations of sexual abuse by paedophile priests, and later attempts to clear the Vatican's bank from its reputation as a money-laundering haven.

Benedict XVI also had troubled relations with other faiths.

Muslims were enraged by his 2006 Regensburg lecture, which quoted - but did not endorse - a Byzantine emperor who called Islam "evil and inhuman." Jews did not appreciate his overtures to the Society of Saint Pius X, a renegade Catholic group linked to anti-Semitism.

In the final months of his papacy, the Vatican was engulfed by the VatiLeaks scandal, a leak of internal documents by the pope's butler suggesting that all sorts of shenanigans were taking place behind Benedict's back.

"A weak point of mine is perhaps my lack of resolve in governing and taking decisions," Benedict said in "Last Testament," a 2016 book interview. "Practical government is not my strong point and that is a weakness. But I can't see myself as a failure," he added.

Unlike Pope Saint John Paul II and Francis, the shy and avuncular Benedict did not have the people's touch, and attracted unfavourable nicknames in the press, such as "Panzer Kardinal," or "God's Rottweiler."

But his intellectual standing was so high that the Ratzinger prize, awarded annually by the Vatican's Ratzinger Foundation, is considered akin to a Nobel Prize in theology. "He has influenced generations of theologians and Christians of every age," the foundation says.

Born on April 16, 1927 in Marktl am Inn, a small town in Bavaria, southern Germany, Joseph Aloisius Ratzinger was the third and youngest child of Joseph Ratzinger, a police officer, and his wife Maria. His older brother Georg is also a priest.

Though his father bitterly resented Nazism, Ratzinger was forced to join the Hitler Youth and was drafted into an anti-aircraft battery late during World War II.

After the war, he studied philosophy and theology at the University of Munich and was ordained a priest on June 29, 1951. Two years later he obtained a theology doctorate, which led to a prestigious career at the universities of Bonn, Muenster, Tubingen and Regensburg.

Initially a liberal theologian, Ratzinger took part as a consultant in the Second Vatican Council of 1962-65, which ushered in major changes in the Catholic Church. His stance became increasingly traditionalist from the late 1960s.

In 1977, he was appointed archbishop of Munich and Freising and proclaimed a cardinal by Pope Paul VI.

In 1981, John Paul II named him prefect of the Congregation for Doctrine of the Faith, the office responsible for punishing child molesters in the clergy. As cardinal and later pope, Ratzinger took the issue seriously, but his clean-up action was not decisive.

The eighth German to become pope in the 2000-year history of Catholicism, and the second non-Italian in nearly 500 years, Ratzinger chose the name Benedict in honour of St Benedict, the 5th century founder of European monasticism.

Upon retiring, Benedict took on the novel title of pope emeritus, pledging to "remain hidden to the world," and never challenged the authority of his successor, disappointing conservatives rattled by Francis' unorthodox style and relatively liberal leanings.

However, a rare and controversial foray into the public sphere in April 2019 saw Benedict blame the Catholic Church's child sexual abuse crisis on the sexual revolution of the 1960s and Western society's growing secularisation.

Some saw the comments as covert criticism of Francis, as they came in the wake of a major Vatican summit in which the current pope identified other causes for the paedophilia scandal, such as institutional failings and the church's cover-up culture.

Francis had previously hailed Benedict as "a wise grandfather" whom he could always turn to for advice. "If I have a difficulty, or something I do not understand, I can call him on the phone: 'Tell me, can I do this?'" he once said.

Benedict spent his last years in relative seclusion in the Mater Ecclesiae (Mother of the Church) Monastery inside the Vatican's walls, attended by private secretary Archbishop Georg Ganswein.

On Wednesday, Francis described Benedict as being "very sick" and he urged the faithful to ask God "to comfort and support" the retired pontiff.

Australian Associated Press