In the early hours of 26 April 1986, reactor four at Ukraine's Chernobyl nuclear power plant began to fail. The following sequence of events resulted in the world's largest ever nuclear disaster, with the fallout from the reactor travelling far beyond the borders of the Soviet Union.
Fifteen years on, BBC News Online looks back at the disaster itself and examines the fate of the people and the countryside closest to it.
April 1986
The Soviet authorities imposed a danger zone around Chernobyl
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In the first of two reports from the time, the BBC's Brian Hanrahan talks over pictures released by the Soviet Union from inside the danger zone. At this time the government were saying that a catastrophe was "no longer possible".
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First pictures of the explosion site
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The Soviet authorities release the first footage of the plant after the accident. They are reported as blaming the western media for blowing the accident out of proportion.
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December 2000
Pollution still contaminates land as far away as Scotland
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14 years after the catastrophic events of April 1986, Ukraine's government finally bows to international pressure, closing Chernobyl's nuclear power station for good. However, the closure brings little comfort to the victims of the disaster, as the BBC's Rob Parsons reports.
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April 2001
The suffering continues for the people of Belarus, Russia and the Ukraine
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On the 15th anniversary of the nuclear explosion, the United Nations appeals for funds to help the victims. While billions of dollars have been pledged to make the reactor safe, the UN says not enough is being done for those who live with the legacy of the disaster, as the BBC's Mike Donkin reports.
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The forgotten fallout - Eyewitnesses
Russian nuclear expert at the scene of the explosion
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The BBC's Robin Aitken travelled to Chernobyl to meet some of the surviving so called 'liquidators' - those who helped in the immediate aftermath of the disaster and were exposed to the worst effects of the radiation.
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The forgotten fallout - Health
Babies' health has been affected
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It is estimated that five million people were exposed to radiation from Chernobyl. The health consequences of the disaster are still with us - especially long term problems. Robin Aitken reports on a slow motion health catastrophe.
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The forgotten fallout - Environment
Exclusion zone around Chernobyl
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Huge swathes of the Ukraine, Belarus and Russia were contaminated by radioactive fallout from Chernobyl. The consequences have been disastrous. Robin Aitken examines the plant's legacy for the countryside that surrounds it.
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The forgotten fallout - Fears
Worker in reactor number three
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Closure of the plant is hugely symbolic for the west, but for the people who still work in and around the plant, the end of Chernobyl will bring yet more upheaval and change. The BBC's Robin Aitken reports.
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