After the emergency shutdown of two reactors in the Russian-occupied Zaporizhia nuclear power plant, Ukrainian President Volodymyr Zelenskyy called for more vigorous international intervention.
The International Atomic Energy Agency (IAEA) and other organizations would have to act much faster than before, Zelenskyy said in his evening video address in Kyiv on Thursday.
"Every minute that the Russian military stays at the nuclear power plant means the risk of a global radiation catastrophe," he said.
Because the power supply failed twice, two of the plant's reactor blocks shut down on Thursday.
A Russian diplomat announced that an expert mission from the IAEA would visit the plant in late August or early September.
Friday marks the 184th day of Ukraine's defense against Russian invasion.
It is dependent on armaments supplies from abroad.
Germany wants to continue to act "prudently and carefully considered" with its aid, said Chancellor Olaf Scholz (SPD) in Magdeburg.
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The IAEA in Vienna, citing information from Kyiv, said the safety system at the power plant in Zaporizhia had shut down two reactors that were running.
The nuclear power plant was further supplied via the power line of a nearby thermal power plant.
It is now reconnected to the Ukrainian power grid.
According to Ukrainian information, all six reactors are currently idle, it said.
The Russian occupation administration, on the other hand, had announced that a reactor block had been restarted.
IAEA Director Rafael Grossi confirmed his willingness to go to Zaporizhia with experts within a few days.
A Russian diplomat at the United Nations put late August or early September as the time to travel.
He is optimistic about the preparations, he said on Russian television.
However, the delegation's itinerary and the necessary security guarantees on both sides have been the subject of arguments for weeks.
The situation in Europe's largest nuclear power plant and its surroundings has been opaque for weeks.
Russia and Ukraine accuse each other of shelling the nuclear power plant.
The UK Ministry of Defense released satellite photos purportedly showing Russian military trucks next to a reactor.
Last week, unverified video also showed military vehicles in one of the large machine shops.
US warns Russia: Electricity from Zaporizhia belongs to Ukraine
According to the Ukrainian operator Enerhoatom, Zaporizhia was cut off from the Ukrainian grid for the first time in its history due to the power outage.
There are also fears that Russia could feed the nuclear power plant's electricity production into its grid.
This would be unacceptable, it said from the United States.
"To be clear, the nuclear power plant and the electricity it produces belong to Ukraine," a US State Department official said.