People in the former Soviet Union have been commemorating the victims of the disaster at the Chernobyl nuclear plant 18 years ago.
Up to seven million people were affected by the disaster
There were memorial services across Ukraine, Belarus and Russia, where millions were affected by the blast.
Some experts say the shelter constructed over the damaged reactor needs urgent repairs, but Ukraine denies any serious safety threat.
Many injured or displaced people still complain about inadequate benefits.
Sergei Shvetsov, head of Russia's Chernobyl Union, said the 40,000 people resident in Russia who were disabled by the disaster were seeing their welfare benefits effectively reduced each year.
But Russian news agencies reported that President Vladimir Putin had signed a law index-linking benefits for Chernobyl victims to inflation.
Hundreds of people attended a memorial service in a small chapel for the victims in the Ukrainian capital Kiev, where some placed flowers and photos of dead relatives.
"Each year, there are fewer of us to attend this service," 40-year-old Tatyana Lazarenko, who was evacuated from the nearby town of Pripyat following the disaster, told AFP news agency.
"I lost a town, friends, people who were close to me. We all had health problems because of radiation," she said.
Another service took place in the town of Slavutich, built to house Chernobyl workers displaced by the accident.
Governments in the region estimate that up to seven million people were affected by the accident.
There has been a dramatic increase in the number of thyroid cancers and leukaemias, as well as birth defects, especially in Belarus.
However, the BBC's Steven Eke says the region is also affected by a serious ongoing lifestyle-related health crisis, and it is difficult to establish exactly how many people have died as a result of the nuclear accident.
The Chernobyl plant remained in service until December 2000, when it was finally shut down under pressure form the world's richest nations.