Ukraine accused Russian forces on Tuesday of blowing up a large dam and a hydroelectric plant in a part of southern Ukraine controlled by Russia, risking massive flooding. Ukrainian authorities ordered hundreds of thousands of residents living along the river to evacuate.
Russian officials said the Kakhovka dam was damaged by Ukrainian military strikes in the disputed area.
The consequences can be far-reaching: flooding of homes, roads and businesses downstream; lowering upstream water levels that help cool Europe's largest nuclear power plant; and depleting drinking water supplies in the south in Crimea, which Russia illegally annexed.
The destruction of the dam added a complex new element to Russia's war in Ukraine, now in its 16th month, as Ukrainian forces are seen pushing ahead with a long-awaited counteroffensive in an area of more than a thousand kilometers of the front line in the east and south of Ukraine.
Ukraine's nuclear operator Energoatom said in a statement on the Telegram network that the dam explosion "may have negative consequences for the Zaporizhia nuclear power plant", near the dam, but for now the situation is "controllable".
The International Atomic Energy Agency tweeted that its experts were closely monitoring the situation at the plant and that there was "no immediate nuclear safety risk" at the facility.
According to the Working Group on the Environmental Consequences of the War in Ukraine, a complete collapse of the dam would take away most of the left bank, and a large drop in the reservoir has the potential to leave the nuclear plant without essential cooling, as well as dry up water supplies in northern Crimea.
Mykhailo Podolyak, a senior adviser to President Volodymyr Zelenskyy, said "a global ecological disaster is unfolding now and thousands of animals and ecosystems will be destroyed in the coming hours."
President Zelenskyy called an emergency meeting of the Security Council to address the crisis, Ukrainian officials said.
"Russian terrorists," wrote President Zelenskyy on Twitter, stressing that the destruction of the dam "only confirms to the whole world that they must be removed from every corner of Ukrainian land."
Ukraine controls five of the six dams along the Dnipro River, which runs from its northern border with Belarus to the Black Sea and is essential to the country's drinking water and energy supply.