UKRAINIAN President Volodymyr Zelensky said Russian forces are trying to seize the Chernobyl nuclear plant.
The plant was the site of the world’s worst nuclear accident when a nuclear reactor exploded in April 1986, spewing radioactive waste across Europe.
The plant lies 130 kilometres (80 miles) north of the capital Kyiv.
The exploded reactor has been covered by a protective shelter to prevent radiation leak and the entire plant has been decommissioned.
Zelensky said on Twitter that “our defenders are giving their lives so that the tragedy of 1986 will not be repeated”.
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He added that “this is a declaration of war against the whole of Europe”.
It comes as Russia has launched a wide-ranging attack on Ukraine, hitting cities and bases with air strikes or shelling, as civilians piled into trains and cars to flee.
Ukraine’s government said Russian tanks and troops rolled across the border in a “full-scale war” that could rewrite the geopolitical order and whose fallout has already reverberated around the world.
In unleashing Moscow’s most aggressive action since the Soviet invasion of Afghanistan in 1979, President Vladimir Putin deflected global condemnation and cascading new sanctions – and chillingly referred to his country’s nuclear arsenal.
This photo shows a view of the city of Kyiv, Ukraine
He threatened any foreign country attempting to interfere with “consequences you have never seen”.
Ukraine’s president said forces were battling other troops just miles from Kyiv for control of a strategic airport.
Large explosions were heard in the capital and in other cities, and people massed in train stations and took to roads, as the government said the former Soviet republic was seeing a long-anticipated invasion from the east, north and south.
The chief of the Nato alliance said the “brutal act of war” shattered peace in Europe, joining a chorus of world leaders who decried the attack, which could cause massive casualties, topple Ukraine’s democratically elected government and upend the post-Cold War security order.
The conflict was already shaking global financial markets – stocks plunged and oil prices soared amid concerns that heating bills and food prices would skyrocket.
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Damaged radar arrays and other equipment is seen at Ukrainian military facility outside Mariupol, Ukraine
Condemnation rained down not only from the US and Europe, but from South Korea, Australia and beyond – and many governments readied new sanctions.
Even friendly leaders such as Hungary’s Viktor Orban sought to distance themselves from Putin.
Ukrainian President Volodymyr Zelensky cut diplomatic ties with Moscow and declared martial law.
“As of today, our countries are on different sides of world history,” Zelensky tweeted.
“Russia has embarked on a path of evil, but Ukraine is defending itself and won’t give up its freedom.”