Dozens of mourners gathered in the Ukrainian capital on Saturday to mark 22 years since the Chernobyl nuclear disaster.
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Holding candles and portraits of relatives, the mourners laid flowers at a memorial to victims of the accident.
Reactor No. 4 at Chernobyl, in what is now northern Ukraine, exploded on April 26, 1986, spewing radiation over a large swath of the former Soviet Union and much of northern Europe in the world's worst nuclear accident. An area roughly half the size of Italy was contaminated, forcing the resettlement of hundreds of thousands of people.
President Viktor Yushchenko and other top officials prayed and lit candles before dawn Saturday to mark the precise time the reactor exploded.
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At first, Soviet leaders tried to cover up the accident. Only on April 28, after scientists in Sweden detected radioactivity, did the Kremlin acknowledge an accident had occurred. But even then, the traditional May Day parades went ahead and millions filled the streets unaware of the invisible fallout.
"This is a day of the biggest sorrow for us, we all have lost our husbands," said Olga Kravchenko, 65, crying and holding a portrait of her husband Mykola who was among the first rescuers on the scene after the accident.
In the first two months after the disaster, 31 people died from exposure to radioactivity, but there is heated debate over the subsequent toll. The U.N. health agency estimates that about 9,300 people will eventually die from cancers caused by Chernobyl's radiation. Some groups, such as Greenpeace, insist the toll could be 10 times higher.
Chernobyl was shut down in 2000 and work is under way on a larger and stronger shelter over the ruins of the exploded reactor.