Pope Francis has celebrated mass with millions of singing and cheering Catholics in the Philippine capital, in one of the world’s biggest outpourings of papal devotion.

Rain fell steadily in Manila in the hours before the mass on Sunday but Filipinos are famous for practising a passionate brand of Catholicism and they turned out in a joyous mood that defied the gloomy skies.

The 78-year-old pontiff thrilled crowds on his way to the bayside park venue for mass.

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He travelled along a motorcade route in a “popemobile” styled after the Philippines’ iconic minibuses known as jeepneys.

The pontiff, dressed in a plastic yellow disposable poncho, waved and smiled to cheering crowds that were 20-deep.

The popemobile stopped repeatedly so he could lean over barriers and kiss babies.

He than arrived to a sea of devoted followers for a mass expected to last two hours.

The Philippines is the Catholic Church’s bastion in Asia, with 80 per cent of the former Spanish colony followers of the faith, and he is a revered figure.

“We are devotees of the Pope,” Bernie Nacario, 53, said as he stood amid a mass of people with his wife and two young children near Rizal Park ahead of the mass.

“The Pope is an instrument of the Lord and if you are able to communicate with him, it is just like talking to God himself.”

As groups of friends sang nearby and others burst into spontaneous cheers, Nacario said he was a long-time arthritis sufferer but today his pain had disappeared.

“It is as if the Lord has cured my ailment.”

Organisers said they were preparing for a record-breaking crowd of up to six million.

Huge crowd gathers for Pope Francis’ last mass in Manila http://t.co/1CydtHYxyz pic.twitter.com/SenYCbwRWP

— Yahoo Philippines (@YahooPH) January 18, 2015

While there were no immediate official estimates of the crowd size, aerial footage showed masses of people surrounding the park and nearby areas.

If the turnout is as big as expected, it would surpass the previous record for a papal gathering of five million during a mass by John Paul II at the same venue in 1995.

Before the mass Pope Francis had an emotional encounter with former street children.

Glyzelle Palomar, a 12-year-old taken in by a church charity, wept as she asked how God could allow children to descend into prostitution and drug addiction.

The Pope enfolded her in his arms, and discarded his prepared speech as he reverted to his native Spanish to deliver an impromptu and heartfelt response.

“She is the only one who has put a question for which there is no answer and she wasn’t even able to express it in words but in tears,” he told those gathered at a Catholic university in Manila.

-AAP