It comes after Ukraine's state energy company said a worker at the Zaporizhzhia plant was wounded in Russian shelling on Saturday evening.
UN chief Antonio Guterres has called for the end of military operations around Europe's largest nuclear plant.
Zaporizhzhia in southern Ukraine has been hit by a series of bombardments since last Friday, with both Russian and Ukrainian forces blaming one another for the attacks.
"Any attack on nuclear power plants is a suicidal thing," the UN's secretary-general told reporters in Tokyo, adding that international inspectors should be allowed to access the nuclear plant immediately.
"I hope that these attacks will end," said Guterres. "At the same time, I hope that the IAEA [International Atomic Energy Agency] will be able to access the power plant."
These remarks by the UN chief come as Ukraine's state energy company said on Sunday that a worker at the Zaporizhzhia plant was wounded in Russian shelling on Saturday evening.
Radiation monitoring sensors were also damaged, Energoatom said.
Speaking in Toyoko, Guterres echoed warnings he made earlier last week about nuclear risks to humanity, which he said was only "a misunderstanding" away from nuclear annihilation.
The Zaporizhzhia plant was captured by Russian forces in the opening stage of the Ukraine war but is still run by Ukrainian workers.
The plant was also shelled on Friday, with Russia again blaming Ukraine for the incident.
The head of the International Atomic Energy Agency (IAEA) raised grave concerns on Saturday about shelling the previous day at Zaporizhzhia, warning of a potential "nuclear disaster".
"I’m extremely concerned by the shelling yesterday at Europe’s largest nuclear power plant, which underlines the very real risk of a nuclear disaster that could threaten public health and the environment in Ukraine and beyond," Rafael Mariano Grossi wrote in a statement on the IAEA website.
"The IAEA has received information about this serious situation – the latest in a long line of increasingly alarming reports from all sides."
Grossi repeated his appeal on Sunday for an IAEA team to travel to Zaporizhzhia.
"This mission would play a crucial role in helping to stabilise the nuclear safety and security situation there, as we have at the Chornobyl nuclear power plant and elsewhere in Ukraine in recent months," he said.
Friday's shelling of a high-voltage power line at the nuclear facility prompted operators to disconnect a reactor, despite no radioactive leak being detected.
Both sides accused each other on Saturday of engaging in "nuclear terrorism". Ukraine's state nuclear power company Energoatom blamed Russia for the damage while Russia's defence ministry accused Ukrainian forces of shelling the plant.
The EU's foreign policy chief Josep Borrell condemned Russian military activities around the Zaporizhzhia plant as "a serious and irresponsible breach of nuclear safety rules and another example of Russia’s disregard for international norms".