Lord Mayor Christy Burke was confronted by a group of protesters objecting to him commemorating the war dead at yesterday's Remembrance Sunday service.
As the former Sinn Fein councillor arrived at St Patrick's Cathedral for the event, he was accused of commemorating those who had killed Irish people.
One protester, who identified himself as Bill O'Brien, told the Lord Mayor as he arrived: "I don't think you should be here."
But the Lord Mayor replied: "I commemorate all men and women who died in wars - every one of them. I commemorate all men and women. The Good Friday Agreement proved that.
"You're dealing with someone who has been in jail, an IRA volunteer, on the run and involved in the struggle from start to finish, so don't go there with me. It's as simple as that."
Labour leader Joan Burton and Fianna Fail leader Micheal Martin also attended the event where President Michael D Higgins was represented by aide de camp Col Brendan McAndrew.
Meanwhile, Ireland's ambassador to Britain became the first Irish diplomat to lay a wreath at the Cenotaph in London since 1946 when Ireland was still a member of the Commonwealth.
The wreath-laying was the latest in a line of symbolic gestures by both the UK and Ireland aimed at putting a troubled history behind them.
During Queen Elizabeth's historic visit to Ireland in 2011 she attended commemorations for both the war dead and those Irish who had died fighting against Britain for independence.
Some 200,000 Irish-born soldiers from north and south served in the First World War, with around 50,000 losing their lives.
But those who returned from the fighting found a country riven by its own conflict with Britain. The War of Independence would follow and by 1921 the island was partitioned.
For decades the newly-formed state struggled with its people's role fighting for Britain in the war.
Returning soldiers were effectively ostracised and were afraid to admit they had taken part in the conflict.
Taoiseach Enda Kenny accepted an invitation for the third year in a row to attend the Remembrance Sunday event in Enniskillen, the scene of the IRA's 1987 Poppy Day bombing, while the Foreign Affairs Minister Charlie Flanagan was present at the event in Belfast.
Mr Kenny welcomed the Irish contribution to the ceremony in London.
"This is all part of the process of uniting the people both east and west and north and south," and that is significant," he said.
Northern Ireland Secretary Theresa Villiers also praised the gesture.
"I think it's a great step forward that the Irish ambassador has laid a wreath at the Cenotaph," she said after attending commemorations in Belfast.