Pope Benedict XVI appeared today to defy predictions that his election as head of the Roman Catholic Church marked a renewed era of rigid central rule and conservative orthodoxy.

Celebrating mass in the Sistine Chapel before the cardinals who elected him yesterday to succeed John Paul II, the former Joseph Ratzinger said that his "primary task" as pontiff would be to work to reunify all Christians.

He also promised to continue the implementation of the reforms of the Second Vatican Council, including the promotion of "collegiality" - allowing local authorities and bishops greater power within the church.

Both pledges fly in the face of suggestions that the cardinals' decision to elevate their German colleague signalled a desire to stick to the hardline traditionalism of his predecessor.

As prefect of the Congregation for the Doctrine of the Faith - the former Inquisition - Cardinal Ratzinger has been the Vatican's chief theological enforcer since 1981, much criticised among Catholic reformers for his absolutist stance on issues such as homosexuality, priestly celibacy and the use of condoms to fight HIV/Aids.

He has also raised the ire of Anglicans by dismissing non-Catholic Christian denominations as "not proper churches"

But in today's homily, delivered in Latin according to tradition, Benedict committed himself to the process of ecumenicism, or dialogue between Christian churches and said that John Paul II had left behind him "a freer, more courageous and younger Church".

"Confounding all my expectations, divine providence through the votes of the venerable father cardinals has called me to succeed this great pope," he said.

"One on 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 added: "The current successor of (Saint) Peter ... is willing to do everything in his power to promote the fundamental cause of ecumenism. Theological dialogue is necessary, the deep study of historic reasons behind past decisions is also indispensable."

The cardinals' choice was greeted warmly by Christian conservatives around the world and political leaders lined up to offer their congratulations to the new pontiff.

President Bush, who clashed with John Paul II over the US-led war on Iraq, said that Benedict was a man of "great wisdom and knowledge". Tony Blair said he looked forward to working with him on issues including Africa and international development.

Beijing, however, which does not recognise his primacy over an official Church, immediately called on him to sever ties with Taiwan and stay out of its internal affairs.

Italian newspapers said that the swift conclusion of the papal conclave after only four votes suggested that Cardinal Ratzinger had exploited the momentum of his front-runner status before Church moderates could unite around one candidate.

But friends and colleagues said that the world had yet to see the warmer side of the man dubbed "God's Rottweiler" or "Cardinal No". "You have to be slow to make a judgement," said Cardinal Edward Egan of New York. "This is really a wonderful, calm, thoughtful human being."

Some of the most negative reaction to the Pope's election came from his native Germany. He is the first German to be elected Pope since the 11th century.

While the tabloid Bild blared "We are the Pope!", the left-wing Berlin daily Tageszeitung blacked out its front page except for the words, "Ratzinger the New Pope - Oh, Mein Gott!"

The Pope's brother, retired priest Georg, told German television that he was "shocked" by his brother's elevation. "I’d thought that his age and not very stable health were a reason for the cardinals to choose someone else," he said.

Bishop Wolfgang Huber, head of the country’s Protestant Church, said Cardinal Ratzinger had treated other religious organisations with a "considerable degree of exclusion and prejudice" in the past.

Bernd Goehring of German ecumenical group Kirche von Unten added: "We consider the election of Ratzinger is a catastrophe. It is very disappointing, even if it was predictable. We can expect no reform from him in the coming years."

But Cardinal Karl Lehmann, the Bishop of Mainz, said his colleague's election was a sign of the country's return into the worldwide community of people after the Nazi Holocaust. "This can give our country heart in many respects," he said.

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