Europe could be hit by a devastating radiation leak from the Chernobyl nuclear site after Russian troops cut off the electricity, Ukraine has warned. Ukrainian Foreign Minister Dmytro Kuleba said on Wednesday that Russia must urgently observe a temporary ceasefire to allow repairs on a power line to the Chernobyl nuclear power plant, saying radiation could be leaked if an electricity outage continues.

The plant, which was stormed by Russian forces last month, has no power supply after troops cut lines connecting it to the national grid on Wednesday.

Emergency diesel generators are supplying back-up power to cool spent fuel rods in a waste store, but they will last only 48 hours, officials said.

Ukrainian Foreign Minister Dmytro Kuleba warned: "After that, cooling systems of the storage facility for spent nuclear fuel will stop, making radiation leaks imminent."

Earlier Ukraine's state-run nuclear company said if the power outage causes a leak it could send sending radioactive material into the air.

Energoatom warned: "The radioactive cloud could be carried by wind to other regions of Ukraine, Belarus, Russia, and Europe."

The company said there are about 20,000 spent fuel assemblies which cannot be kept cool amid the power outage.

Without electricity, experts fear the ventilation systems at the plant will also stop working - exposing staff to dangerous doses of radiation.

Mr Kuleba called for an urgent ceasefire from Russia so engineers can go in to restore the vital power lines.

UN watchdog the International Atomic Energy Agency said Russia had "violated the key safety pillar on ensuring uninterrupted power supply".