Ukrainian President Petro Poroshenko has compared the April 26, 1986 Chernobyl nuclear disaster with the ongoing crisis in Ukraine's east, adding that "Russia is conducting an undeclared war against his country."
Poroshenko spoke at the defunct nuclear power plant, where he and Belarusian President Alyaksandr Lukashenka lamented the "unhealing wound" inflicted by the Soviet-era accident 31 years ago and commemorated its victims.
"We again have buried thousands of people. Again we have hundreds of thousands of displaced people," Poroshenko said, referring to the conflict with Russia-backed separatists that has killed more than 9,900 people in eastern Ukraine since 2014.
"I am confident that together, we will defeat that demon as well," he said.
Lukashenka voiced solidarity, saying that "Belarusians are and will always be your reliable friends" -- a tacit reassurance that while Belarus is Russia's ally, it is also wary of Moscow and does not support Russia's infringements on Ukraine's territorial integrity.
Reactor No. 4 at the power plant north of Kyiv, in then-Soviet Ukraine exploded at 1:23 a.m. on April 26, 1986, after a safety test went wrong.
About 30 people died in the immediate aftermath and thousands more are feared to have died in the years that followed from the effects of the disaster, which spread radiation across parts of Ukraine, Belarus, Russia, and large swaths of Europe.
PHOTO GALLERY: Russian Photographer Recalls Death, Beauty Inside Chernobyl's Fourth Reactor (Click To Open)
The precise number of victims and extent of the damage remains the subject of debate, in part because the Soviet authorities took days to publicly acknowledge the disaster and kept information hidden.
Last year, the crumbling "sarcophagus" used to contain radiation from the smoldering reactor at the time was replaced with a 2.3-billion-dollar metal dome in a bid to stop future leaks. More than 200 tons of uranium remain buried inside.
Two years before the Soviet Union withdrew its troops from Afghanistan following a losing war of occupation, the Chernobyl disaster was in retrospect another sign of the weaknesses of the communist giant that collapsed in 1991.
Poroshenko called it "an unhealing wound that we live with as a people."
"Perhaps more than anyone else, the Chernobyl tragedy affected our Belarusian brothers," he said, referring to the fact that winds blew radiation northward into Belarus, where some its strongest effects were felt.
"Both Belarusians and Ukrainians know that the Chernobyl catastrophe knows no borders," Lukashenka said.
Ukrainian Prime Minister Volodymyr Hroysman paid tribute to the Chernobyl "liquidators" -- emergency workers, state employees, and others sent into clean up after the disaster with little or no preparation, protective gear, or information about the gruesome dangers they faced.
"Thank you to the heroes who, at the expense of their own lives and health, protected us from the horrible consequences of this tragedy," Hroysman wrote on Facebook.
Meanwhile, some 400 protesters marched in Minsk on April 26 to protest the construction of a nuclear power plant in the Ostrovets district of the western Hrodno region, RFE/RL's Belarus Service reported.
The first unit of the plant, being built in conjunction with Russia's Atomstroyexport, is due to be finished in 2019.