Benedict XVI has celebrated his first Mass as Pope, vowing to strive for the unity of all Christians.
Pope Benedict XVI will be inaugurated on Sunday
Marking the start of his pontificate at the Vatican's Sistine Chapel, he said he felt inadequate at the responsibility of leading the Church.
The former Cardinal Joseph Ratzinger was elected head of the Roman Catholic Church on Tuesday.
He said his first planned overseas trip will be a return to his native Germany, for a youth conference in August.
He will be inaugurated as the 265th pope on Sunday, the Vatican has announced.
Pope Benedict XVI, 78, and his cardinals processed into the Sistine Chapel on Wednesday morning, where they stood beneath Michelangelo's Last Judgement.
The Pope wore the papal mitre, carried a pastoral staff and made the sign of the cross, before going on to say Mass in Latin.
It was a private ceremony for the cardinals who elected him, but was broadcast on TV around the world.
In a message ending the Mass he said: "On one hand I have a sense of inadequacy and human turmoil at the responsibility entrusted to me yesterday... on the other hand, I feel living in me a deep gratitude to God who does not abandon his flock but guides them always."
He said he believed his predecessor John Paul II was holding his hand.
Benedict said his first job was to unify all Christians, but also said he was committed to "open and sincere dialogue" with followers of other religions.
The Pope will return to Germany in August
He said his election had "confounded all my expectations".
He finished his message by offering a blessing for all those watching the ceremony on television.
The new Pope had been one of the front runners in the papal election, which began on Monday when the 115 voting cardinals were sequestered in the Sistine Chapel for their secret conclave.
The name Benedict comes from the Latin for "blessing" and the last pope bearing the name, Benedict XV, reigned during World War I.
Pope Benedict XVI, who is the oldest man to become pope for more than a century, was born in 1927 into a traditional farming family in Bavaria, Germany, although his father was a policeman.
The future pope's studies at seminary were interrupted by World War II and his supporters say that his experiences under the Nazi regime convinced him that the Church had to stand up for truth and freedom.
He is the first German pope since the 11th Century.
The BBC's Ray Furlong in Berlin says Cardinal Ratzinger's election as Pope will generate amazement and enthusiasm in Germany as well as concern among those who had hoped for a more liberal pontiff.
A close friend and confidant of Pope John Paul II, Pope Benedict XVI is also known as a fellow conservative.
For more than 20 years he was head of the congregation of the Doctrine of the Faith in the Vatican - the Vatican's guardian of orthodoxy.
The BBC's William Horsley in Rome says his papacy is sure to continue John Paul II's strongly traditional interpretation of the Catholic faith, including opposition to abortion, homosexuality, priestly marriage and women priests.
Our correspondent says that the homily he made at the Mass before the start of the Conclave in which he denounced all deviations from traditional Church teachings as trickery and error, may have been decisive in winning his election.