International Atomic Energy Agency (IAEA) staff must be able to access all nuclear facilities in Ukraine in a timely and safe manner and "without impediment", said the G7 Non-Proliferation Directors Group in a statement.

Personnel from the IAEA should also be allowed to "engage directly, and without interference, with the Ukrainian personnel responsible for operating these facilities", they added.

Russian armed forces' continued control of the plant posed a "serious threat" to the "safety and security of these facilities", they said.

"These actions significantly raise the risk of a nuclear accident or incident and endanger the population of Ukraine, neighbouring states, and the international community," they warned.

The atomic plant should not be used for military activities or the storage of military material, said the group.