The Taoiseach led the Irish tributes to Brother Roger, saying he was "shocked and saddened" at the violent death of the Taizé Community's founder.
"The contribution of this remarkable religious community towards reconciliation and understanding was widely appreciated," Mr Ahern said.
"It has drawn thousands of young people from many nations and cultures to experience afresh the joy of worshipping God together."
Britain's Archbishop of Canterbury, Dr Rowan Williams - spiritual head of the world's 77 million Anglicans - called the killing "an indescribable shock", adding: "Brother Roger was one of the best-loved Christian leaders of our time, and hundreds of thousands will be feeling his loss very personally."
The Church of Ireland Archbishop of Dublin, Dr John Neill, praised the dead man's work in promoting ecumenism.
"Brother Roger personally, and through the community which he founded, made a profound contribution to the ecumenical movement through a place of prayer and of worship to which millions have been drawn, young and old, Christian and non-Christian alike.
"In that holy place, lives have been touched and Christ has been found. May he rejoice today in the presence of the Christ whom he so faithfully served."
The Catholic Bishop of Clogher and chairman of the Irish Bishop's Conference Commission on Communications, Dr Joseph Duffy, expressed the shock of his fellow bishops, but hoped that Brother Roger would now "enjoy, for eternity, the peace and intimacy with God which so marked his earthly life.
"Although he died as a result of a violent attack, his life was one of complete commitment to a peaceful and united world," Dr Duffy said.
"This was never more evident than when he was joined daily, by thousands of young people of different faiths, themselves searching for that vision.
"Brother Roger was one of the great religious figures of the 20th century. His legacy will continue to live in the music associated with Taizé, in the many local prayer groups in Ireland and across the world which have taken Taizé as their model, but most of all in his unique vision of a united and reconciled world."
A Dublin priest, Fr Dan Joe O'Mahony OFM Cap, said "thousands upon thousands" of Irish people had made the trip to Taizé over the years, as he himself had done twice. Brother Roger's death was an "unmerciful shock", akin to the gun attack on John Paul II. "He was a towering figure, but also a very gentle man," Fr O'Mahony said.
A memorial service for Brother Roger is to be held at 8pm on Friday, September 16th, at the Pro-Cathedral in Dublin.
