VATICAN CITY - Pope Francis on Saturday soldiered through a more than 2-hour Easter Vigil Mass in St Peter's Basilica, one of the longest services in Catholic liturgy, amid renewed concerns about the 87-year-old's frail condition.

His voice at times sounded raspy and out of breath, but he read out all of his prepared texts, including a more than one-page long homily, and he smiled and waved at the congregation as he left in a wheelchair.

In other occasions, Pope Francis has delegated longer readings to aides.

On Friday, the pope skipped at the last minute the night-time Via Crucis (Way of the Cross) procession at Rome's Colosseum in what the Vatican said was a bid to "preserve his health" ahead of other Holy Week events.

The surprise move came after weeks in which Francis repeatedly limited his public speaking and canceled engagements while struggling with what has been described as colds, bronchitis and the flu.

The pope is also restricted in his mobility due to a knee ailment, and regularly uses a wheelchair or a cane.

Pope Francis looked in better shape on Thursday as he performed a foot-washing ceremony in a women's prison, recalling Jesus' gesture of humility to his apostles at the Last Supper, and at a Good Friday service in St Peter's.

Holy Week consists of several solemn ceremonies leading to Easter on Sunday, the most important festivity in the Christian calendar, celebrating the day in which the faithful believe Jesus rose from the dead.

Saturday's evening service, held in Christendom's largest church, started in near total darkness before lights were turned on, signifying the passage from darkness to light when the Bible says Jesus rose from the dead.

It was attended by about 6,000 people, the Vatican said.

In his homily, recalling that the stone sealing Jesus' tomb was rolled back as he was resurrected, Pope Francis urged Christians to keep their faith even when weighed down by sorrow, fear or other adversities.

He mentioned, among other things, "the rubber walls of selfishness and indifference that hold us back in the effort to build more just and humane cities and societies," as well as "all our aspirations for peace that are shattered by cruel hatred and the brutality of war."

Pope Francis is set to conclude Easter celebrations on Sunday with Mass in St. Peter's Square and his twice-annual "Urbi et Orbi" (to the city and the world) blessing and message from the central balcony of St. Peter's Basilica. —Reuters