President Mary McAleese has paid tribute to Nobel Peace Prize winner Martti Ahtisaari for his work in verifying that IRA arms were put beyond use.
Prof McAleese said his work had "rightly earned him the gratitude of the Irish people".
“The conferring of this prestigious award is a fitting recognition of the outstanding work of this quiet, unassuming champion of peace over many years in seeking to bring to an end to several difficult and intractable conflicts," she added.
“His work with (South African politician) Cyril Ramaposa in verifying that IRA arms were put beyond use has rightly earned him the gratitude of the Irish people.”
A former arms inspector and ex-president of Finland, Mr Ahtisaari oversaw the decommissioning of IRA arms in the North and went on to play a vital role in mediating conflict in Indonesia and tackling humanitarian crisis in the Horn of Africa.
The laureate, 71, won a gold medal, diploma and €1m, the Nobel Foundation announced in Oslo today.
The North's First Minister Peter Robinson said: “This is recognition for a man who over three decades has been working towards resolving conflicts across the world including here in Northern Ireland.”
Deputy First Minister Martin McGuinness added: “Martti Ahtisaari has earned a reputation as a diplomat of exceptional talent. From the horn of Africa throughout Europe, Asia and of course here in Ireland his efforts have contributed greatly to bringing peace to many regions riven by conflict.”
The Nobel committee commended Mr Ahtisaari for his “important efforts, on several continents and over more than three decades, to resolve international conflicts”.
Mr Ahtisaari and Cyril Ramaposa carried out a series of inspections of IRA dumps after their 2000 appointment.
Mr Ahtisaari is international advisor to the independent Consultative Group on the Past headed by former Church of Ireland Primate Robin Eames and Ex-Policing Board vice-chairman Denis Bradley.
They said: “We are delighted that our colleague has been awarded this prestigious honour. This is hugely deserved for his work, not just in Northern Ireland, but throughout the world.
“Martti’s experience has been invaluable to us in finding a way to deal with the legacy of Northern Ireland’s troubled past.”
SDLP leader Mark Durkan said his readiness to aid peace anywhere in the world would have been a decisive factor for the Nobel committee.
“This award is for a statesman whose talents have helped to reduce conflict, secure peace or build confidence and understanding in a number of troubled areas of the world,” he said. “His credibility was also a help at a time of problems in our own process.”
Sinn Féin president Gerry Adams said: “He played a positive and constructive role in the Irish peace process along with Cyril Ramaphosa.
“He is known not only for this but for his hard work, that is acknowledged today, in building peace around the world.”