Pope Benedict XVI led the world's Catholics in Good Friday ceremonies clouded by growing Vatican concern over the fate of Christians in the Middle East and perceived threats to its teachings.

The German pope, who turns 85 on April 16, presided over a sung ceremony in St. Peter's basilica commemorating the last hours of Jesus Christ's life on a day that also marks the start of Jewish Passover celebrations.

While the pontiff appeared frail and tired after his trip to Mexico and Cuba last month. He has nevertheless been taking part in Holy Week with his characteristic spiritual vigour, on Thursday a stinging rebuke to rebellious priests on Thursday.

The pope's personal preacher, Father Raniero Cantalamessa, in his Good Friday prayers also made an apparent reference to the wave of clerical child abuse scandals that have shaken the Catholic Church in recent years. Cantalamessa referred to the "sufferings of innocent children" and said that "many atrocious crimes have recently remained unsolved," urging abusers to "confess their crimes" and "not to take their secrets to the tomb."

Friday's Vatican prayers will be followed by the Via Crucis (Stations of the Cross) ceremony -- a re-enactment of Christ's crucifixion -- to be held by the Colosseum, where thousands of Christians were martyred in Roman times. The commemorations were mirrored around the world -- from the sight of Catholic fanatics in the Philippines having themselves nailed to crosses in a bloody display of religious frenzy to the crowds of pilgrims in Jerusalem.

In Cuba, state-run television broadcast a Good Friday ceremony held in Havana cathedral for the first time in more than 50 years following an explicit request from the pope during his visit to the Communist island. In Jerusalem's Old City, processions commemorated Christ's crucifixion.

Pilgrims -- some of them carrying crosses -- walked from the Franciscan Monastery of the Flagellation along the path where Jesus is believed to have walked, now known as the "Via Dolorosa" or the "Way of Suffering."

Easter ceremonies traditionally stress the suffering of the Catholic Church and the world, an emphasis that is being particularly keenly felt this year with multiple conflicts around the world and tensions within the Church.

The pope on Thursday issued a rare rebuke, condemning those who questioned the Church's teachings on clerical celibacy and the ordination of women. The Catholic Church was "in an often dramatic situation", he said.

"Recently, a group of priests in a European country published an appeal for disobedience, giving concrete examples of how to be disobedient," he added, responding to a call made by a group of Austrian priests last year.

This year's prayers for the Stations of the Cross will also emphasise the sense of crisis for traditional family values -- a subject close to the pope's heart as shown in frequent denunciations of gay marriage and divorce.

"There have been so many blows for our families! So many separations, betrayals! And then divorces, abortions, abandonments!" reads one of the prayers, published by the Vatican's official daily, L'Osservatore Romano.

The Holy Week celebrations take place amid concerns over the fate of Christians in the Middle East in the face of rising Islamism and violent conflict, especially in Syria which has a large Christian minority.

Donations from a Vatican mass on Thursday went to Syrian war victims and the pope has made a personal donation of $100,000 (77,000 euros) to the same cause.

AFP