Families bereaved by the Omagh bomb have supported an appeal for money for the Manchester victims.
The 1998 blast was the single most bloody attack of the Troubles and killed 29 people after a dissident republican car bomb exploded on a busy shopping street.
Michael Gallagher lost his son Aiden, 21, and extended the hand of friendship across the Irish Sea.
Mr Gallagher said: "We know many of the trials and tribulations that the families affected by the Manchester bomb will go through.
"In a situation that is totally despairing I think there is great hope in the fact that the people of Manchester from right across the communities of all religions have come together, have sent a very positive message and not allowed this individual, whether working alone or with others, to poison the community by bringing out racial hatred which these things often do.
"I think that is a very powerful message."
He said he coped with his own tragedy by focusing on the goodness of his murdered son, a young mechanic and only son who had gone to a shop to buy some clothes, rather than concentrating on those responsible.
The bomb devastated Omagh town centre just months after the 1998 Good Friday Agreement sealed the North's emergence from conflict.
It was blamed on the Real IRA and in 2009 four men were held responsible in a civil case brought by families of the victims.
Mr Gallagher said he felt helpless in recent days, being unable to attend rallies in Manchester to show solidarity.
"Generally the families that have not been affected would not be listening to news and keeping a close eye as we would on what is happening.
"It is important that they concentrate on the wonderful people that they lost and what I have found in my experience I had to dig very deep inside my soul to have the strength to carry on and it was all the good things, all the good people I met in life, the good person that Aiden was, that is what gave me the strength and energy to go forward."
He said the Omagh families had supported an appeal for money for the families and hoped others would too.
"This is something that has been thrust on a family who never in their wildest dreams could ever imagine, their lives being turned upside down by their children going to a concert.
"So it is difficult but I would say, don't concentrate on the individual who committed this atrocity because that is exactly what they want you to do.
"They want hatred to build up inside people and cause community strife and that is the last thing we need.
"We need to show a united front that our democracy, our freedom and our humanity will not be affected by their acts no matter how brutal they are."