In pictures: World bids farewell to Pope Francis

Presidents, royalty and simple mourners bade farewell to Pope Francis on Saturday at a solemn funeral ceremony, where a cardinal appealed for the pontiff's legacy of caring for migrants, the downtrodden and the environment to be kept alive.

The Argentine pope, who reigned for 12 years, died at the age of 88 on Monday after suffering a stroke.

The Vatican estimated more than 250,000 people attended the ceremony, cramming the square and the roads around.

Aerial views of the Vatican showed a patchwork of colours - black from the dark garb of the world's leaders, red from the vestments of some 250 cardinals, the purple worn by some of the 400 bishops and the white worn by 4,000 attending priests.

After the funeral, as the great bells of St. Peter's pealed in mourning, the coffin was placed on an open-topped popemobile and driven through the heart of Rome to St. Mary Major Basilica.

Francis, who shunned much of the pomp and privilege of the papacy during his 12-year reign, had asked to be buried there rather than in the crypt of St. Peter's, which is the traditional resting place for popes.

The burial itself was being conducted in strict privacy.

The popemobile left the Vatican from the Perugino Gate, a side entrance just yards away from the Santa Marta guesthouse where Francis had chosen to live , instead of the ornate Renaissance apartments in the papal palace.

Crowds estimated by police as numbering some 150,000 lined the 5.5-km (3.4-mile) route to St. Mary Major.

Some waved signs and others threw flowers towards the casket. They shouted "viva il papa" (long live the pope) and "ciao, Francesco" (goodbye, Francis) as the procession made its way around Rome's ancient monuments, including the Colosseum.

Francis' death ushered in a meticulously planned period of transition, marked by ancient ritual, pomp and mourning. Over the past three days, around 250,000 people filed past his open coffin, laid out before the altar of the cavernous basilica.

Choirs at the funeral sang Latin hymns and prayers were recited in various languages, including Italian, Spanish, Chinese, Portuguese and Arabic, reflecting the global reach of the 1.4-billion-member Roman Catholic Church.

Many of the faithful camped out to try to secure spots at the front of the crowd, while others hur ried there in the early morning.

Francis, the first non-European pope for almost 13 centuries, battled to reshape the Church, siding with the poor and marginalised, while challenging wealthy nations to help migrants and reverse climate change.

Traditionalists pushed back at his efforts to make the Church more transparent, while his pleas for an end to conflict, divisions and rampant capitalism often fell on deaf ears.

The pope carried his desire for greater simplicity into his funeral, having rewritten the elaborate, book-long funeral rites used previously.

He also opted to forego a centuries-old practice of burying popes in three interlocking caskets made of cypress, lead and oak.

Instead, he was placed in a single, zinc-lined wooden coffin.

He will be the first pope to be buried outside the Vatican in more than a century.

His tomb has just "Franciscus", his name in Latin, inscribed on the top. A reproduction of the simple, iron-plated cross he used to wear around his neck hangs above the marble slab.