VATICAN CITY -- Pope Francis washed the feet of 12 prisoners Thursday and urged them to serve one another as brothers, as he ushered in the solemn pre-Easter rituals made more poignant this year following the devastation of Paris' Notre Dame Cathedral.

Francis travelled to a prison in Velletri, outside Rome, for the Holy Thursday service that re-enacts the biblical story of Christ washing the feet of his disciples. The Mass opens the most solemn period in the liturgical calendar, leading up to the commemoration of Christ's crucifixion on Good Friday and resurrection on Easter.

Francis has frequently performed the Holy Thursday ceremony at prisons to reinforce his message that even the most important figures must serve the most marginal like slaves, as Jesus did in washing the feet of his disciples.

"The bishop isn't the most important. The bishop must be the most servant-like," Francis said.

Directing his message at the prisoners themselves, Francis urged them to not try to dominate one another, and to make the fights that break out between them a "fleeting thing."

"The biggest must serve the smallest. He who feels biggest must be the servant," Francis said. "May this gesture that I make help us to be more servant-like with one another, more friendly, brothers in service."

He then proceeded to wash, dry and kiss the feet of the inmates: nine Italians, and one each from Brazil, Ivory Coast and Morocco. Francis, who suffers from sciatica, needed help from his aides to stand up and kneel down before each prisoner.

This year, the final days of Holy Week have taken on particular resonance following the fire at Notre Dame, a symbol of French Catholicism.

Francis has offered his condolences repeatedly to the French faithful, and French President Emmanuel Macron said Thursday that during a call to Francis after the blaze, he had invited the pontiff to visit Paris. On Wednesday, Francis fielded a call from U.S. President Donald Trump offering the sympathy of the American people over the loss, the Vatican spokesman said.

Francis started the day by celebrating the Chrism Mass to bless the holy oils that will be used during the year.

On Friday, he presides over the Way of the Cross procession at Rome's Colosseum re-enacting Christ's crucifixion, followed by the Easter Vigil in St. Peter's Basilica and Easter Sunday in a flower-decked St. Peter's Square.

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This version corrects the spelling of Chrism.