ALMATY -- The 35th anniversary of the Chernobyl catastrophe in Ukraine last month has re-opened old wounds for the people of Kazakhstan, which for more than 40 years hosted the Soviet Union's primary nuclear weapons testing site.
The Semipalatinsk nuclear testing site in northeast Kazakhstan operated from 1949 to 1991, when the Soviet Union collapsed.
But the ramifications from the site -- including dire consequences for the environment and for the health of local residents -- are still being felt and will continue to be for many years to come, observers say.
'History does not go backwards'
To commemorate the anniversary of the Chernobyl disaster, Ukrainian President Volodymyr Zelenskyy visited the "exclusion zone" on April 26 and made remarks urging the international community to work together to guarantee global nuclear security.
The exclusion zone is an area spanning a 30km radius around the nuclear power plant that was evacuated in the aftermath of the accident on April 26, 1986. Ukrainian authorities have deemed the area unsafe for human habitation for 24,000 years.
"Our task is to do everything possible to bolster security and strengthen safety to avoid and never repeat a similar disaster in the future," Zelenskyy said.
"History does not go backwards," he said in his televised speech, "so Chernobyl today is a common challenge and a joint responsibility for the future and safety of the planet."
Doctors directly linked 30 deaths to the explosion. But thousands more are feared to have died in the years that followed from radiation poisoning across Ukraine as well as in neighbouring Russia and Belarus.
The exact number of victims remains a subject of intense debate because Soviet authorities hid most of the information about the disaster.
About 600,000 emergency workers and state employees who became known as "liquidators" were dispatched with little or no protective gear to help clean up the aftermath of the disaster.
Up to 4,000 people could eventually perish from the invisible poison in Ukraine, Russia and Belarus, a 2005 United Nations report estimated.
In November 2016, workers built a massive metal dome over the remains of the reactor -- paid for with €2.1 billion ($2.5 billion) in international funding -- to stop future leaks and ensure the safety of Europeans for generations.
Ukraine's security service on April 26 announced the release of a cache of archival documents, confirming that Soviet authorities hushed up at least three accidents at the Chernobyl plant in 1982 and 1984.
The Chernobyl power plant and two others in present-day Russia with the same reactors were the "most dangerous" nuclear power plants in the USSR and continued operations could have "threatening consequences", according to KGB documents from 1983.
'A great tragedy'
The Soviet Union began to actively build up its nuclear potential after World War II.
The Semipalatinsk test site (also known as "the Polygon") in northeast Kazakhstan, about 130km from the city of Semipalatinsk (now called Semey), was the Soviet Union's first and one of the largest nuclear test sites -- and was conveniently far from Moscow.
From 1949 to 1989, authorities carried out about 460 nuclear tests there, a combination of atmospheric and underground tests.
The total power of the tested nuclear charges was 2,500 times higher than the power of the bomb dropped on Hiroshima.
Soviet authorities assured local residents that these tests were harmless, but in reality the explosions caused cracks and fissures that regularly leaked radioactive gases beyond the test site, polluting vast areas in eastern Kazakhstan.
In August 1956, an above-ground test in Semipalatinsk caused more than 600 residents of Ust-Kamenogorsk, a city about 400km east of the test site, to be hospitalised for radiation sickness, the British scientific journal Nature reported in 2019.
After that, the Soviet military created a secret medical centre to care for such patients -- and to serve as a base for collecting medical data on those exposed to radiation.
To hide the purpose of the clinic, according to Nature, the Soviets called it "Anti-Brucellosis Dispensary No. 4", referring to a bacterial disease spread by farm animals.
Those who sought medical help received examinations but never a real diagnosis, according to the article.
After the fall of the Soviet Union, authorities destroyed many medical records and sent other classified files to Moscow.
The dispensary was renamed the Scientific Research Institute of Radiation Medicine and Ecology (IRME), but even today's researchers do not know the contents of the Soviet records.
About 1.5 million Semey residents were exposed to radioactive substances, say Kazakh health organisations.
"The Polygon tests were a great tragedy," said Talgat Muldagaliyev, deputy director of IRME in Semey.
"But we can't go back. Now we need to study the consequences," he told the journal.
Worse than Chernobyl
Semipalatinsk provides exceptional evidence of how carelessly the Soviet authorities treated Kazakhs' lives and health, analysts say.
The Polygon is the world's only nuclear test site whose territory included residential areas, said Dmitry Kalmykov, director of development at the Karaganda Ecological Museum.
"Even though nuclear explosions were regularly carried out at the test site, Soviet authorities did not trouble themselves to relocate local residents," he said.
"Those who had the opportunity moved on their own, but many families were forced to stay."
Several thousand Kazakhs still inhabit the territory covered by the test site, he said.
Semipalatinsk had worse consequences than even Chernobyl did, said Zarema Shaukenova, director of the Kazakhstan Institute for Strategic Studies.
"The explosion at Chernobyl ... was a terrible but still a one-time catastrophe, but the population of the provinces of Kazakhstan near the test site was irradiated for several decades in a row," she told the KazInform news agency.
"The Semipalatinsk test site and its research base provided what the Soviet Union proudly called the 'nuclear missile shield of the Motherland'," she said.
But the price for such security, particularly for Kazakhs, was too high, she added.
That is why Kazakhstan, supported by its neighbours in Central Asia, initiated the creation of a nuclear-free zone in the region, Shaukenova said.
Leaders of the five Central Asian countries signed the agreement in 2006 in Semey. It took effect in March 2009.
'Nowhere to go'
In the past, Moscow strictly censored media coverage or discussion of the consequences of the nuclear explosions, but today Kazakh citizens and analysts speak openly about the problem.
Many residents of the region still suffer from serious illnesses and children are often born with defects, said Nazira Ormanbayeva, who moved to Almaty from Semey 16 years ago.
Ormanbayeva's grandfather died of stomach cancer when she was a small child. Doctors called radiation the "rather likely" cause of the cancer, she said, quoting her father.
He was only 56.
Semey has a ghastly anatomical museum at the medical university, where stillborn babies with terrible defects -- victims of nuclear tests -- are exhibited, she said.
"I always wanted to leave there so my children would grow up in environmentally safe conditions," said Ormanbayeva.
"I feel sorry for those who still live there, because they have nowhere to go."