Ukrainians have marked 29 years since the Chernobyl nuclear disaster, laying wreaths and candles near the plant where work to lay a new seal over the reactor site has been delayed.
The explosion of reactor number four on April 26, 1986, spewed poisonous radiation over large parts of Europe, particularly Ukraine, Belarus and Russia.
At 1.23am, the exact time of the explosion, hundreds of people placed flowers and candles in the dark at the foot of a monument in Slavutych, a town 50km from the plant.
Slavutych was built to rehouse Chernobyl workers who had lived near the plant and were forced to move further away after the disaster.
At the site of the plant itself, about 100km from Kiev, Ukraine’s president Poroshenko laid a wreath on Sunday at a monument to the victims.
The human toll of the disaster is still disputed.
United Nations experts officially recognised 31 deaths among plant workers and firefighters directly linked to the blast.
But environmental group Greenpeace predicted that there would be some 100,000 additional cancer deaths caused by the disaster.
The Soviet authorities of the time dispatched hundreds of thousands of people without proper protection to put out the fire and clean the site.
They hastily laid over the reactor site a concrete cover dubbed ‘the sarcophagus’, which is now cracking and must be replaced.
Poroshenko on Sunday inspected ongoing work to lay a new 20,000-tonne steel cover – a project estimated to cost more than two billion euros ($A2.8 billion).