The European Union has asked the UN nuclear watchdog to safeguard Ukraine's nuclear plants, two of which are now under Russian control, and mobilise international help in case of an emergency, according to a letter seen by Reuters.
Russian forces have seized Ukraine's Zaporizhzhia nuclear power plant, Europe' biggest, and the spent-fuel and radioactive waste facilities at Chernobyl, next to the now defunct power plant where the world's worst nuclear accident happened in 1986.
"I... request that IAEA does its utmost to ensure the nuclear safety of Ukraine's nuclear facilities under the current conditions of war," EU energy policy chief Kadri Simson wrote in a letter to International Atomic Energy Agency (IAEA) director Rafael Grossi.
Russia "should immediately cease its violent actions against Ukraine and first and foremost return all of Ukraine's nuclear facilities to the full operational and regulatory control of Ukraine," said the letter, dated March 4 and seen by Reuters.
Ukrainian authorities said Russian forces had seized control of Zaporizhzhia on Friday after setting an adjacent training facility on fire. Russia's defence ministry blamed the attack on Ukrainian saboteurs.
Russian forces have since placed staff running the facility under their command and restricted communications with the outside world - developments the IAEA said on Sunday it was "extremely concerned" about.
While the fire at Zaporizhzhia was quickly extinguished and there was no damage to its reactors, it highlighted concerns about the potentially disastrous consequences should the conflict damage one of Ukraine's four operating nuclear power plants.
Simson called on the IAEA to mobilise the international community "to be ready to provide Ukraine with assistance in case of an emergency".
Ukrainian power producer DTEK called on Sunday for Western countries, NATO and the UN to introduce no-fly zones over Ukraine's nuclear power plants.
The EU is preparing to urgently link Europe's electricity system to Ukraine's grid, which would allow Ukraine to receive emergency power from Europe if military attacks caused power outages.