Pope Francis died on Monday aged 88, prompting mourning across the Christian world for the energetic reformer who inspired devotion from Catholics but riled traditionalists during a 12-year papacy.

Mourners gathered, many in tears, in St Peter's Square, where just a day earlier the the frail-looking pontiff had greeted worshippers on Easter Sunday, having recently left hospital following a 38-day battle with double pneumonia.

World leaders paid tribute to Francis' moral and spiritual leadership and countries began preparations to mark his death, which will now set off a succession scramble among Cardinals to see who next will lead the world's 1.4 billion Catholics.

"Dearest brothers and sisters, it is with deep sorrow that I must announce the death of our Holy Father Francis," said Cardinal Kevin Farrell in a Vatican statement.

"This morning at 7:35 am (0535 GMT) the Bishop of Rome, Francis, returned to the home of the Father.

"His entire life was dedicated to the service of the Lord and His church," said the statement, released shortly before 10:00 am.

- St Peter's Square prayers -

His death sets in motion centuries-old traditions that will culminate in the gathering of a conclave of cardinals to choose a successor.

In the next four to six days the Vatican's cardinals will decide on the pope's funeral date, which must take place between four and six days after his death.

In the meantime, the day-to-day running of the tiny Vatican City state will be handled by the Camerlengo, a senior cardinal, who is currently Dublin-born Cardinal Farrell.

Francis died in his apartment at the Saint Martha residence where he had lived since his election in March, 2013, the Vatican said.

The cause of his death would "probably" be shared after Francis's........

© Al Monitor