Experts say that Ukraine's occupied Zaporizhzhia nuclear power plant — Europe's biggest — is "extremely vulnerable" to meltdown after the head of the International Atomic Energy Agency (IAEA) said all safety measures had been "violated" by Russian forces.

If the plant loses grid power due to a potential uptick of fighting in the area, backup generators and batteries are still insufficient to cool, not only the six reactors, but large pools of highly radioactive spent fuel, said Shaun Burnie, nuclear specialist with Greenpeace East Asia.

Adding to these concerns is news that Russian forces are using Zaporizhzhia as a weapons depot and a cover for launching attacks. US Secretary of State, Anthony Blinken, said that Russia was using the nuclear site as the "equivalent of a human shield" at a UN meeting on nuclear non-proliferation this week.

Using the plant in this way violates the Geneva Convention, which states that particular care must be taken if "installations containing dangerous forces" are located near fighting. Around 500 Russian troops are reported to be currently located at the site.

When fighting first broke out in the vicinity of the plant in early March, it was the first time in the atomic age that war had come so close to a major facility.

Once Russian forces occupied the power plant in mid-March and allowed Ukrainian staff to carry on their work, news from Zaporizhzhia, which currently operates three of its reactors, had been intermittent.

Nuclear safety 'violated' by Russian occupiers

Now, however, concern is mounting again that the plant is not being sufficiently maintained.

"[It is a] violation of every possible nuclear safety measure that you can imagine," said Rafael Grossi, director general of the International Atomic Energy Agency (IAEA), in an interview with DW on Friday.

"Is it true that there is explosives and other material stocked near the reactors?" he asked of reports that missiles and other weapons could be launched from the site, with counter-attack impossible due to the extreme threat of an accident.

Grossi of the IAEA is also concerned that the Ukrainian staff who are under the command of the Russian occupiers at Zaporizhzhia are unable to properly carry out their duties and have faced threats of violence.

"I have been trying to put together a technical mission led by myself to go there to address a number of issues," he told DW. But access will be impossible without the accompaniment of UN peacekeepers, he said, a situation he is discussing with UN Secretary-General, Antonio Guterres.

In an interview with AP published Tuesday, Grossi said the atomic energy agency has only "patchy" contact with staff at the site. He was also concerned that necessary equipment, including spare parts for maintenance of the reactors, was not being delivered due to interrupted supply chains.

"We are not sure the plant is getting all it needs," he said, adding that the situation is "completely out of control."

Plant still 'extremely vulnerable'

Greenpeace's Shaun Burnie agrees that it is vital that trained local staff maintain their positions and can work safely at the nuclear site. While Russia has more than twice as many reactors as Ukraine, most are older models, meaning their engineers don't have the expertise to run the newer technology in Zaporizhzhia, he said.

Local staff will also be needed in the event of the regular flooding from the Dnieper River, which flows through the vicinity of the Zaporizhzhia plant and could damage the dams and reservoirs that provide the cooling water for the reactors.

Petro Kotin, head of Ukraine's state-run nuclear power plant operator Energoatom, last week accused Russia of abducting up to 100 employees from Zaporizhzhia.

"Only some of these people then return to work with a broken psyche, making a statement that they love the Russian world because of the tortures that are applied to them by the invaders," Kotin said.

Burnie is doubly concerned after a recent visit to survey the formerly Russian army-occupied Chernobyl nuclear plant, site of the world's worst nuclear disaster in 1986.

There his team discovered a contaminated exclusion zone riddled with landmines — which stopped effective monitoring of the area. In addition, vital monitoring equipment in the Chernobyl plant had been destroyed, damaged or stolen during the Russian military occupation.

Meanwhile, Energoatom's Petro Kotin has been calling for the liberation of the Zaporizhzhia plant from the Russian "invaders," saying that Russian president Vladimir Putin is engaging in "nuclear terrorism."