Those affected by the 1998 Omagh bombing are being invited to participate in a public inquiry into the atrocity.
Scottish judge Lord Turnbull, who chairs the inquiry, said he needed to fully understand the significance of the bombing and its impact.
The Omagh Bombing Inquiry will host four weeks of commemorative and personal statement hearings in January and February of next year.
The inquiry is probing whether the 1998 Real IRA massacre, which claimed 29 lives, including a woman pregnant with twins, could have been prevented by British state authorities.
It was established after a High Court judgment recommended a public inquiry into alleged security failings in the lead-up to the atrocity.
The Dublin government has formally agreed to provide assistance to the inquiry, which held its first public hearing in July.
In an open letter, Lord Turnbull said the “tragic bombing of Omagh caused untold damage to the town and wider communities”.
He added: “Thirty-one lives were lost, hundreds of people were injured and the bombing caused significant damage to businesses and property across the town.
“These figures alone, however, do not truly reveal the damage that the bombing caused and the real-life human impact.”
Lord Turnbull said the purpose of the hearings in January and February would be to commemorate those who were killed and also to hear personal statements of people who were affected.
He said: “This can include people who were injured, both physically and psychologically, those who responded in formal roles, local businesses or people who witnessed the events.
“When I opened the Inquiry earlier this year I said that I wanted to hear directly from those most affected by the bombing.
“Today I am inviting anyone who wishes to share their experiences with the inquiry to complete a personal statement on how they were affected by the bombing.
“All of your experiences are important.”
Lord Turnbull said there is no obligation for anyone to participate, nor do people need to give oral evidence at the hearings.
He added: “If you wish to share your experience all you need to do is complete a personal statement form, which is available on the inquiry website.
“There are no rules about how you write your statement. It should reflect your own personal experience.
“Not everyone who submits a personal statement will be asked to provide oral evidence at the commemorative hearings in January and February, and there will be no obligation to give evidence if you would prefer not to.
“But I will read every statement, and your experiences will help to inform the direction and approach of the inquiry.
“I fully understand what a difficult topic this is and the real risk this inquiry bears in bringing back the trauma of what happened in Omagh in 1998.
“The Inquiry is also working with Wave Trauma Centre to provide emotional or wellbeing support for those wishing to engage with the inquiry.”
Lord Turnbull added: “There have been many investigations into the terrible events of 15 August 1998.
“My inquiry may be the final opportunity to get to the truth of whether the bombing could have been prevented by the UK state.
“The experiences of those most affected on the day will be invaluable in helping me do so.”
