Mourners in Belarus, Russia and Ukraine are marking the 20th anniversary of the world's worst nuclear accident at Chernobyl, with day-long ceremonies and vigils honoring the millions of people affected by the disaster. The pre-dawn explosion, sparked by a failed experiment, hurled radiation across vast parts of the three former Soviet republics, as well as large parts of Europe.
Bells tolled and sirens blared at the now-closed Chernobyl nuclear power plant in Ukraine at the exact time two explosions rocked reactor number four, spewing a huge radioactive cloud into the air, 20 years ago.
In the capital, Kiev, mourners joined a solemn gathering of dignitaries to place red candles and carnations beside stone burial slabs engraved with pictures of the dead. Orthodox priests led the mourners in prayers, punctuated by tears.
In neighboring Russia, President Vladimir Putin honored so-called liquidators, men who were sent in virtually unprotected to deal with the disaster's clean-up at great risk to their lives.
In a Kremlin ceremony broadcast on Russian television, President Putin said the men's selflessness helped to save many lives.
The exact death toll resulting from the world's worst nuclear disaster may never be known. Within days of the accident, at least 50 died from radiation exposure, but thousands have since developed life-threatening diseases caused by radiation exposure. Estimates say that from 9,000 to 90,000 may eventually suffer health problems or die prematurely because of the accident. Hundreds of thousands of others were forced to leave their homes behind forever.
Opening an international conference in Kiev earlier this week, Ukrainian President Viktor Yushchenko appealed to the world's wealthiest nations to again contribute to the cost of cleaning up the disaster. Mr. Yushchenko says Kiev anticipates the cost will reach $170 billion by 2015.
The president says one of the biggest expected outlays is for the second sarcophagus, or protective shell over the plant. Experts say the shell is urgently needed to prevent a possible second catastrophe at Chernobyl.
Belarus, which was directly downwind of the radiation fall-out, suffered some of the worst effects. There, President Alexander Lukashenko is expected to spend the day touring villages and farms, in a bid to press his policy of rehabilitating affected areas. The policy is viewed as controversial by some, who believe the land remains far too polluted for human settlement.
Opposition groups in Belarus are expected to hold what has become an annual demonstration in the capital to protest what it says was the government's mishandling of Chernobyl's aftermath.
This year's demonstration takes on heightened significance as it could signal whether the political opposition can advance the momentum it gained during last month's unprecedented weeklong protests against Mr. Lukashenko's government.