G7 nations said on Wednesday they were “profoundly concerned” by the threat to the safety of Ukraine's nuclear power plants triggered by the war with Russia.
The group's foreign ministers said the seizure of nuclear sites and other actions by Russia significantly raised the risk of an accident at one of the sensitive sites in Ukraine.
They called on Russia to hand back control of the Zaporizhzhia plant, which is near the front line of recent fighting and which the two sides accuse each other of shelling.
As the focus of the war moves south, Ukraine on Wednesday remained coy about a mystery explosion at a Russian air base in Crimea - in what would mark a major escalation of the war if Ukraine was behind it.
Control of the Black Sea coast has taken on a global significance because of the grain exports heading to the Mediterranean - although Ukrainian diplomats said on Wednesday that the first shipment to Lebanon had been rejected.
"The buyer in Lebanon refused to accept the cargo due to delays in delivery terms," said the Ukrainian embassy in Beirut.
Ukraine said 13 civilians had died near Zaporizhzhia and accused Russia of using its nuclear reactors as a shield by firing from the area in the knowledge that Ukraine would be reluctant to shoot back.
“The cowardly Russians can't do anything more, so they strike towns ignobly hiding at the Zaporizhzhia atomic power station,” said Andriy Yermak, President Volodymyr Zelenskiy's chief of staff.
Russia denies shelling the nuclear site and claims it is Ukraine that has fired at its own plant. Mikhail Ulyanov, the Russian ambassador to UN institutions in Vienna, said Moscow was seeking a Security Council meeting about events at Zaporizhzhia.
The G7 ministers did not assign blame for the artillery fire but said Russian actions were endangering the plant.
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“It is Russia’s continued control of the plant that endangers the region,” said the foreign ministers from the US, Britain, Canada, Germany, France, Italy and Japan, and the European Union's top diplomat, in a joint statement.
“We remain profoundly concerned by the serious threat that the seizure of Ukrainian nuclear facilities and other actions by Russian armed forces pose to the safety and security of these facilities, significantly raising the risk of a nuclear accident or incident and endangering the population of Ukraine, neighbouring states and the international community.”
“IAEA staff must be able to access all nuclear facilities in Ukraine safely and without impediment, and engage directly, and without interference, with the Ukrainian personnel responsible for the operation of these facilities.”
UN Secretary General Antonio Guterres on Monday urged the warring parties in Ukraine to step back from the brink of a nuclear catastrophe, describing attacks on the country's atomic plants as “a suicidal thing”.
Russia's movements near the site of the 1986 Chernobyl disaster have also unnerved western officials and led the UN's nuclear inspectors at the International Atomic Energy Agency to dispatch a team to investigate.
The same agency says it wants to send a team to Zaporizhzhia but has not yet been able to gain access — something which the G7 said should change.
