The Catholic Primate, Archbishop Seán Brady, said he was "deeply shocked" at the news of the murder in Burundi of Archbishop Michael Courtney at a village 25 miles south of the capital, Bujumbura.
He said they had been good friends since they were students together at the Irish College in Rome in the 1960s. They had met only a few weeks ago in Rwanda when Archbishop Brady was visiting there as part of a Trócaire delegation.
Extending his sympathy to the Courtney family, he said it was typical of the late Archbishop's "noble, generous spirit that he should have met his death while returning from a pastoral visit to one of the dioceses in Burundi".
In Rome last night, the Coadjutor Archbishop of Dublin, Most Rev Diarmuid Martin, described himself as "absolutely stunned" on hearing of the killing.
The deceased man had been a guest at Archbishop Martin's liturgy of welcome in Dublin last August.
He described his death as "a very nasty piece of work".
Burundi was "a very difficult posting" for Vatican representatives, saying "our people are not well protected there".
He recalled that in 1995 the Archbishop of Gitega in Burundi had also been killed. Archbishop Martin believed his death and the killing of Archbishop Courtney arose from the church's role in trying to bring peace to that troubled country, and that yesterday's assassination was an attempt to disrupt the current peace process there.
He said he knew Archbishop Courtney for many years through the deceased man's work on the Council of Europe and from his assistance during the controversial Cairo population conference in 1994, at which Archbishop Martin represented the Vatican.
Archbishop Courtney was posted to the papal nunciature there. He was "extremely helpful and friendly ... very attentive to people," said Archbishop Martin.
Cardinal Desmond Connell said he was "greatly distressed by the tragic news of the murder", and expressed his deepest sympathy to the Archbishop's family "for whom this news must have come as a devastating shock".
The Taoiseach, Mr Ahern, also expressed his shock and condemned the "horrific attack".
The Minister for Defence and TD for Tipperary North, Mr Smith, said he knew the late Archbishop and admired him greatly. He expressed his shock and sadness. "He faced the real challenges and dangerous situations he encountered with the utmost courage, knowing full well that he was putting his life at risk by carrying out his duties."
He expressed his sympathy to the Archbishop's family and friends, "both here in his home place of Tipperary, and throughout the Catholic community".