Joseph Ratzinger as a German air force assistant during World War II. (AFP)

Berlin, April 20 (Reuters): Joseph Ratzinger, elected Roman Catholic Pope yesterday, served in the Hitler Youth during World War II when membership was compulsory, according to his autobiography.

In Milestones: Memoirs 1927-1977, Ratzinger recounts the onset of the war and his detention as a prisoner of war by US soldiers in 1945.

Ratzinger?s wartime experiences have been a source of controversy in some newspapers which probed the German Pope?s past after Pope John Paul died and he quickly became a frontrunner to succeed the deceased pontiff.

His biographers say he was never a member of the Nazi party and his family opposed Adolf Hitler?s regime. Jewish human rights group, the Simon Wiesenthal Center, have also recognised Ratzinger?s anti-Nazi roots.

?The new Pope, like his predecessor, was deeply influenced by the events of World War II. As a child, Pope Benedict XVI grew up in an anti-Nazi family,? the group said.

Founded in 1922, the Hitler Youth was a paramilitary organisation of the Nazi Party. It was disbanded in 1923 but re-established in 1926, a year after the Nazi Party was recognised.

In his autobiography, Ratzinger said he and his brother Georg were both enrolled in the Hitler Youth when membership was obligatory. John Allen, who wrote a biography of Ratzinger entitled Cardinal Ratzinger: The Vatican's Enforcer of the Faith, quoted his subject as saying that his father?s criticism of the Nazis forced the family to move home four times.

Ratzinger, who turned 16 in 1943, served in an anti-aircraft defence unit. A year later, he was summoned to the military, yet avoided being enrolled into the SS, the Nazi's elite troops, he says, by declaring his intention of becoming a priest.