Catholic Archbishop of Dublin Diarmuid Martin has assured the congregation at the opening mass of the 50th International Eucharistic Congress that the church here is on a path to renewal.

Around 12,500 pilgrims, over a quarter of them from overseas, attended the event in the RDS.

Before the mass there was a celebration of gathering, which welcomed pilgrims from Ireland and around the world.

Dr Martin told the congregation that the last half century of the church's history in Ireland has been marked with the sinful and criminal abuse and neglect of children.

He said the victims were weakest in society and should have been the object of the greatest care and support and Christ-like love.

He prayed for survivors who he said may suffer the effects for the rest of their lives.

Mass was concelebrated by Papal Legate Cardinal Marc Ouellet, Archbishop Diarmuid Martin and Archbishop Piero Marini, President of the Pontifical Committee for IECs, among others. 

In his message, Dr Martin also thanked God for the country's great priests and religious men and women who love the Church and their calling, and who give generously in following Christ.

Dr Martin said "we recall all those who suffered abuse" and in a "spirit of repentance, remember each of them in the silence of our hearts".

Papal Nuncio Archbishop Charles Brown read the letter of appointment from Pope Benedict naming Cardinal Ouellet as his representative at the Congress.

In his homily, Cardinal Ouellet welcomed the faithful from Ireland and around the world.

He thanked priests for their “love and courage” at this difficult time in the purification in the life of the church.

He said the church in Ireland is suffering and is facing new and serious challenges to the faith.

The Congress Bell, which began its pilgrimage on St Patrick's Day in 2011, was rung in a ceremony calling the four ecclesiastical provinces to the Congress, beginning a series of processions from different parishes throughout the country.

A fifth ecclesiastical province was created for the Congress and Bishop Thomas Dabre from India called on the faithful from around the world to join the celebrations as a procession of representatives from the five continents walked through the arena.

Approximately 80,000 people have bought tickets for the final mass at Croke Park next Sunday.

The congress has as its theme "Commmunion with Christ and With One Another".

It will feature a wide selection of masses and other liturgies, along with testimonies from prominent lay and ordained Catholics and other Christians, including the Church of Ireland Archbishop of Dublin, Dr Michael Jackson.

Eucharistic Congresses are held every four years and it is eight decades since the Archdiocese of Dublin last hosted one, attracting an estimated one million people to its final mass.

Earlier today, Dr Martin said the abuse of children in the church here is a travesty of the gospel.

But he said that people have come from all over the world in solidarity with the Irish church to attend the International Eucharistic Congress.

The latest news from the congress will be available throughout the week on RTÉ.ie’s dedicated International Eucharistic Congress 2012 page.