Mourners bearing candles marked the 20th anniversary of the Chernobyl nuclear disaster on Wednesday, honouring those who died from its effects as leaders pledged to ensure it would never happen again.
Hundreds of people, each bearing a candle, some with red carnations, filed slowly through the streets of Slavutych, the town built to house the Chernobyl plant's workers after the world's worst nuclear accident on April 26, 1986.
At 1.23 am Moscow time - a minute before the time of the explosion and subsequent fire that sent radiation billowing throughout Europe - a minute of silence was observed.
A bell tolled and alarm sirens blared.
A middle-aged man, tears welling in his eyes, shook his head in disbelief as he stood alongside younger mourners.
President Viktor Yushchenko was due to place flowers an hour later at a church honouring "liquidators" who died fighting the blaze or later from excessive doses of radiation.
The blast in Chernobyl's fourth reactor contaminated large swaths of territory in Ukraine, Belarus and Russia.
Soviet authorities took two days to inform the world - and their own people. They then launched feverish clean-up and reconstruction efforts culminating in the construction of a structure to house the shattered reactor about 80 km (50 miles) north of Kiev.
The Slavutych procession moved to a memorial, with mourners placing candles at the foot of a wall bearing images graved in stone of engineers and firefighters sent to tackle the blaze.
Estimates of the death toll linked to Chernobyl vary widely.
The World Health Organisation put at 9,000 the number of extra deaths, while the environmental group Greenpeace predicts an eventual death toll of 93,000.
Hundreds of thousands were evacuated and the United Nations estimates seven million still live on land with unsafe radiation levels.
In the run-up to the anniversary, Mr Yushchenko called for new efforts - and more cash - to build a new "sarcophagus" to replace the leaking original containment structure.
International figures said the main lesson was to adopt a common approach to nuclear safety.
Mohamed El-Baradei, head of the International Atomic Energy Agency, which helped investigate the accident, called for closer cooperation "particularly at a time when we are witnessing an expansion of nuclear power to meet increasing energy demands in many parts of the world".
US President George W. Bush paid tribute to "lives lost and communities hurt in the devastation" and pledged efforts to complete construction of a new "sarcophagus".