Memorial services have been held in Ukraine to mark the 30th anniversary of the Chernobyl nuclear disaster. In the early hours of 26 April 1986, a botched test at the nuclear plant in what was then the Soviet Union triggered a meltdown that spewed deadly clouds of radioactive material into the atmosphere, forcing tens of thousands of people from their homes. Relatives of those who died as a result of the world's worst nuclear accident attended a candlelit vigil in a Kiev church, built in their memory.

Chernobyl memorial
A woman cries as she attends a memorial service in KievValentyn Ogirenko/Reuters
Chernobyl memorial
A woman prays during a memorial service for victims of the Chernobyl nuclear disaster in a church in KievValentyn Ogirenko/Reuters
Chernobyl memorial
A Chernobyl monument at St Michael the Archangel Orthodox Church in Kiev is illuminated in the rainBrendan Hoffman/Getty Images
Chernobyl memorial
A woman holds a candle and flowers at a memorial service in KievBrendan Hoffman/Getty Images
Chernobyl memorial
People attend a Chernobyl memorial at St Michael the Archangel Orthodox Church in KievBrendan Hoffman/Getty Images
Chernobyl memorial
People attend a commemoration of the 30th anniversary of the Chernobyl nuclear accident at St Michael the Archangel Orthodox Church in Kiev, UkraineBrendan Hoffman/Getty Images

More than half a million civilian and military personnel were drafted in from across the former Soviet Union as so-called liquidators to clean-up and contain the nuclear fallout, according to the World Health Organisation.

Thirty-one plant workers and firemen died in the immediate aftermath of the accident, most from acute radiation sickness. Over the past three decades, thousands more have succumbed to radiation-related illnesses such as cancer, although the total death toll and long-term health effects remain a subject of intense debate.

Mourners also gathered for a service in Slavutych, a town that was established 50km away from Chernobyl, to house many of the power plant workers and their families who had to leave their homes in Pripyat, forever.

Chernobyl memorial
People prepare to lay a wreath at a memorial in Slavutych, Ukraine, as Orthodox clergymen stand bySean Gallup/Getty Images
Chernobyl memorial
A serviceman stands guard in front of a memorial in Slavutych dedicated to firefighters and workers who died in the Chernobyl nuclear disasterGleb Garanich/Reuters
Chernobyl memorial
Faces of some of the firefighters and workers who died during or after the Chernobyl nuclear disasterGleb Garanich/Reuters
Chernobyl memorial
A man places a flower in front of the monument to Chernobyl victims in SlavutychGenya Savilov/AFP
Chernobyl memorial
Candles set in the shape of a radiation hazard symbol are seen on a square next to the monument to Chernobyl victims in Slavutych, some 50km from the accident siteGenya Savilov/AFP
Chernobyl memorial
Young people lay candles in the pattern of a radioactivity symbol in SlavutychSean Gallup/Getty Images
Chernobyl memorial
People commemorating the 30th anniversary of the Chernobyl nuclear disaster arrive to lay candles and flowers at a memorial in SlavutychSean Gallup/Getty Images

The disaster and the government's reaction highlighted the flaws of the Soviet system with its unaccountable bureaucrats and entrenched culture of secrecy. For example, the evacuation order only came 36 hours after the accident. Former Soviet leader Mikhail Gorbachev has said he considers Chernobyl one of the main nails in the coffin of the Soviet Union, which eventually collapsed in 1991.

The anniversary has garnered extra attention due to the imminent completion of a giant arch that will enclose the stricken reactor site and prevent further leaks for the next 100 years. Even with the new structure, the surrounding exclusion zone – 2,600 square km (1,000 square miles) of forest and marshland on the border of Ukraine and Belarus – will remain uninhabitable and closed to unsanctioned visitors.