"I am no longer the Pope, I am just a pilgrim," declares Pope Benedict XVI as he leaves Vatican City in a white helicopter and steps down from office.

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The first pope to resign in six centuries, Pope Benedict flew past St Peter's Basilica in a white air force helicopter as he left Vatican City - church bells rang out across Rome as he passed overhead.

The head of the Catholic Church has called for unity in the wake of his resignation and pledged his obedience to whoever replaces him.

In what could be his final public address, the pope thanked the faithful for their "friendship", from the balcony at his new temporary residence, the Castel Gandolfo. The speech was also played out on screens across Rome.

"I am no longer the Pope...I am just a pilgrim who is starting the last step of his pilgrimage on earth," he said.

Just before he helicopter took off, the Pope sent his last tweet.

Some in the church fear that Benedict's resignation could lead to a rift among its 1.2bn members, because after his temporary stay at Castel Gandolfo, he will move back into a convent in Vatican City - meaning he will live side-by-side with the new pope.

However Pope Benedict sought to head this off with his emotional farewell at the Vatican's Sala Clementina earlier today.

"May the Lord show you what he wants. Among you there is the future pope, to whom I today declare my unconditional reverence and obedience," he said.

He made the pledge ahead of the closed-doors conclave where cardinals will elect his successor, a key figure as the church continues to deal with the fall-out of sex abuse scandals, falling membership and its treatment of women.

Turbulent seas and rough winds

Benedict himself alluded on Wednesday to the troubles of the church, saying: "I have had moments of joy and light, but also moments that haven't been easy ... moments of turbulent seas and rough winds, as has occurred in the history of the church when it seemed like the Lord was sleeping."

A number of cardinals from the developing world, including Ghanaian Peter Turkson and Antonio Tagle of the Philippines, are thought to be among the leading candidates to be the next pope.

For now though - at least until later tonight - Benedict officially remains in the role. But at 8pm (19.00 GMT), the papacy will become officially vacant and two Swiss Guards who ceremonially watch over the summer villa will march away and not return until the new pope moves in to the hilltop residence - and to Vatican City.

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