President Michael D Higgins and his wife Sabina have led a global candle lighting ceremony to commemorate the 35th anniversary of the Chernobyl nuclear accident.
The president said the disaster had cast a dark shadow across human history, but the Irish response had never faltered and that commitment continues to inspire.
The event is being organised by Chernobyl Children International.
Four years ago, President Higgins became the world's first Head of State to back the United Nations 'Chernobyl Remembrance Day'.
"On International Chernobyl Disaster Remembrance Day, 26 April, we recall that fateful day in April 1986 when the news of the nuclear disaster unfolding in Chernobyl stunned people around the globe."https://t.co/bjIbvKdDGj #Chernobyl35 pic.twitter.com/YLNxnwAWNU— President of Ireland (@PresidentIRL) April 26, 2021
The event was created in memory of those who gave their lives trying to stem the release of radiation from the plant in northern Ukraine, after two catastrophic explosions had exposed the reactor core on 26 April 1986.
To mark the event this year, a global candle lighting event has been organised by Chernobyl Children International.
Its volunteer CEO, Adi Roche, said that while the impact of the Chernobyl disaster can never be undone, significant Irish efforts had alleviated some of the pain and suffering.
In his statement, President Higgins said he wanted to thank all those who have worked tirelessly to help the victims of Chernobyl - bringing hope, compassion and empathy to those whose lives were deeply affected by one of history's worst tragedies.
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More than 25,000 children from the wider Chernobyl area have travelled to Ireland for rest and recuperation; Chernobyl Children International has delivered more than €107million in aid to the region since 1986; and more than 4,000 people in the region have been given life-saving cardiac surgery.
The disaster, which struck during safety test at the plant 110km north of the capital Kiev, forced tens of thousands of people to abandon the area permanently.
Thirty-one plant workers and firemen died in the immediate aftermath of the disaster, mostly from acute radiation sickness.
Thousands more later succumbed to radiation-related illnesses such as cancer, although the total death toll and long-term health effects remain a subject of intense debate.
The Ukranian government has begun a process that could eventually allow it to apply to the United Nations' cultural, scientific and education body for protection of the site.
"We believe that putting Chernobyl on the UNESCO heritage list is a first and important step towards having this great place as a unique destination of interest for the whole of mankind," said Ukrainian Culture Minister Oleksandr Tkachenko.
"The importance of the Chernobyl zone lays far beyond Ukraine's borders ... It is not only about commemoration, but also history and people's rights," he said.
Most of the area around the abandoned nuclear plant is a wilderness of empty buildings, scrubland and rubble.
All of the buildings in Pripyat, a ghost town that was once home to 50,000 people mostly working at the plant, are in need of repair.
Mr Tkachenko said he hoped that Chernobyl, which had already become a popular site for adventure tourists before the coronavirus pandemic prevented most international travel, would bounce back and begin to lure visitors again.
In 2019, the HBO series 'Chernobyl' was behind a jump in the number of visitor to the power plant and nearby Pripyat, with 120,000 people visiting the area.
Additional reporting Reuters