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.

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.

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.