The Pope led the world 's Roman Catholics in Palm Sunday celebrations by paying tribute to those killed for their faith - a reference to the victims of Islamic State militants . Thousands of people , including the 78-year-old Argentine pope and prelates dressed in red vestments , carried palm fronds and branches in St. Peter 's Square on the day that marks the start of Holy Week , which ends on Easter Sunday . In his homily during the Mass that followed , Francis , who last month denounced the killing of 21 Egyptian Coptic Christians by Islamic State militants in Libya , paid tribute to those he said were being killed for their faith today . Scroll down for video . Waving to the faithful : The Pope led the world 's Roman Catholics in Palm Sunday celebrations by paying tribute to those killed for their faith . Thousands of people gathered in St. Peter 's Square in the Vatican City on the day that marks the start of Holy Week , which ends on Easter Sunday . Many of those who attended , including the 78-year-old Argentine pope ( centre ) and prelates dressed in red vestments , carried palm fronds and branches . Speaking out : In his homily during the Mass that followed , Francis paid tribute to those he said were being killed for their faith today . He presided at a colourful procession in St. Peter 's Square . commemorating the day the Bible says people of Jerusalem . welcomed Jesus days before he was crucified . 'We think too of the humiliation endured by all those who , . for their lives of fidelity to the Gospel , encounter . discrimination and pay a personal price , ' he said , speaking in . Italian . 'We think too of our brothers and sisters who are persecuted . because they are Christians , the martyrs of our own time . There . are many of them . They refuse to deny Jesus and they endure . insult and injury with dignity , ' he said . Procession : Cardinals hold palm leaves while Pope Francis leads the Palm Sunday mass at St Peter 's Square at the Vatican on Sunday . Francis presided at a colourful procession in St. Peter 's Squarecommemorating the day the Bible says people of Jerusalem welcomed Jesus days before he was crucified . Leading prayers : Francis ( pictured ) has at times expressed alarm over the rise of Islamic State militants and the plight of Christians in the Middle East . Palm Sunday marks the official beginning of Holy Week during which Christians observe the death of Christ . Francis has at times expressed alarm over the rise of . Islamic State militants and the plight of Christians in the . Middle East . He has said that the international community would be . justified in using military force as a last resort to stop . 'unjust aggression ' but that it should not be up to a single . nation to decide how to intervene in the conflict . The coming week is one of the busiest in the liturgical . calendar for the leader of the world 's 1.2 billion Roman . Catholics . The coming week is one of the busiest in the liturgicalcalendar for the leader of the world 's 1.2 billion Roman Catholics . Cardinals hold palm leaves as Pope Francis leads the Palm Sunday mass at Saint Peter 's Square at the Vatican on Sunday . Huge crowds assembled at St Peter 's Square . Pope Francis used the opportunity to pay tribute to those he said were being killed for their faith . On Holy Thursday , he presides at two services , including one . at a Rome prison where he will wash and kiss the feet of male . and female inmates to commemorate Christ 's gesture of humility . towards his apostles on the night before he died . Francis is the first pope to hold the foot-washing service . outside a church and to include women and Muslims , which has . upset conservative Catholics . He presides at two Good Friday services , including a Via . Crucis ( Way of the Cross ) procession around the Colosseum . After celebrating Easter Eve and Easter Day Masses he . delivers his 'Urbi et Orbi ' ( to the city and the world ) message .
The 78-year-old Argentine pope led the world 's Roman Catholics by paying tribute to those killed for their faith . Last month Pope Francis denounced the killing of 21 Egyptian Coptic Christians by Islamic State militants in Libya . Thousands gathered at Easter Squareon the day that marks the start of Holy Week , which ends on St Peter 's Sunday .