More than 1,000 people have paid tribute to Iraq aid worker Margaret Hassan at a service in the Irish town where her mother was born.
Mrs Hassan and her husband used to holiday in Kenmare, Co Kerry
A video appears to show Irish-born Mrs Hassan being murdered by her kidnappers after being held for a month.
Mourners gathered in Kenmare, County Kerry, on Wednesday, where Mrs Hassan's sister and family still live.
The European Union said the killing would make it almost impossible for relief agencies to continue in Iraq.
Political leaders have condemned the apparent murder of Mrs Hassan, who was director of Care International's Iraq operations.
Mrs Hassan's husband has begged for the return of the body of his wife, who had UK and Iraqi nationality.
At the ecumenical ceremony in the Irish Republic parish priest Father Tom Crean said Mrs Hassan's death had pierced "to the marrow of all our beings".
"Our hearts just cry in pain with Margaret's family," he said, adding they would pray for the return of her body so people could "fully honour and celebrate her life," he said.
The EU's aid commissioner Poul Nielson said the people of Iraq had lost a true friend and humanitarian.
"This kind of savagery makes it almost impossible for relief agencies to continue their crucial work in Iraq," he said.
He said Care has been a long-standing partner of the EU's humanitarian aid office in Iraq.
Responding to news of Mrs Hassan's apparent death Tony Blair said it was "abhorrent", while Irish premier Bertie Ahern said her kidnappers "stand condemned by... the entire international community".
A video showing a blindfolded woman being shot in the head has surfaced and has been checked by experts.
Mr Hassan made an emotional plea for her body to be returned
UK Foreign Secretary Jack Straw said they had concluded Mrs Hassan had "probably" been murdered.
He added: "It is repugnant to commit such a crime against a woman who has spent most of her life working for the good of the people of Iraq."
Mrs Hassan, 59, had lived in Iraq for 30 years.
She was seized by an unknown group in the Iraqi capital on 19 October.
'Repaid with murder'
Arabic TV news channel Al-Jazeera said on Tuesday it had had a copy of the videotape showing Mrs Hassan's apparent killing for several days, but had chosen not to broadcast it.
Mrs Hassan's sisters and brother, Deirdre and Kathryn - who live in London - and Geraldine and Michael Fitzsimons, said in a statement their "hearts are broken".
They said: "We have kept hoping for as long as we could, but we now have to accept that Margaret has probably gone and at last her suffering has ended."
The Muslim Council of Britain expressed its condemnation saying: "Mrs Hassan had served the Iraqi people tirelessly for most of her adult life and it is appalling her goodness has been repaid with murder. "
Mrs Hassan was driving to her job as director of Care International's Iraq operations when she was seized. The agency has since halted work in the country.
If Mrs Hassan's death is confirmed she will be the first foreign female hostage to have been murdered in Iraq.
The only other western woman to known to be currently held in Iraq is Teresa Borcz Khalifa, 54, a Polish-born long-time resident of Iraq who was seized last month.
The body of a woman, believed to be a westerner, was found in Falluja on Sunday, but has not been identified.