The United Nations nuclear watchdog has warned that Russian troops are putting “unbelievable pressure” on workers at the Zaporizhzhya nuclear power plant – which is both the largest in Ukraine and Europe as a whole – saying the situation is “unsustainable.”

Russian forces seized the plant during a dramatic assault on March 4, and they have since then forced Ukrainian plant operators to manage the site under extreme conditions. The UN’s International Atomic Energy Agency has also reported that eight specialists from Rosatom, Russia’s state nuclear corporation, are also onsite.

IAEA director-general, Rafael Grossi, said on April 29 that the agency was informed by Kyiv that the Ukrainian staffers at Zaporizhzhia were being monitored constantly by the Rosatom experts, who demanded daily reports from plant management about “confidential issues” on the functioning of the plant.

“The IAEA considers that the presence of Rosatom senior technical staff could lead to interference with the normal lines of operational command or authority, and potential frictions when it comes to decision-making,” the IAEA said in a report published on Friday.

Early last month, Ukrainian nuclear officials reported that “the morale and the emotional state” of staff at the Zaporizhzhya power station is “very low.”

The Zaporizhzhya Oblast in southeastern Ukraine, where the plant is located, has increasingly fallen into the site of Russian forces as they look to establish control of the neighboring Donbas region.

Ukraine officials warned last week that Russia is looking to establish a referendum to annex occupied territories in Zaporizhzhya and Kherson, which is just south of the nuclear power plant along the Dnipro river.

Grossi, who traveled to Ukraine in March amid the heightened security threat, said the situation at Zaporizhzhya “continues to be challenging and requires continued attention.”

The IAEA chief warned of the circumstances at Zaporizhzhya that the “situation will become unsustainable” and on Friday proposed leading a team to the plant at the “earliest possible opportunity.”

While Ukraine has assured the agency that the integrity of the plant’s six reactors had not been affected and that no radioactive material had been released, Grossi said a visit  Zaporizhzhya was warranted because IAEA specialists “need to see the functionality of the safety equipment” and to check “whether there has been an impact on the physical protection of material” as a result of the Russian attack in March.

Grossi had visited the Chernobyl nuclear power plant last week after it had been occupied by Russian forces for 35 days.

Since the withdrawal of Russian troops from the infamous site of the world’s worst nuclear catastrophe, alarming reports have surfaced reflecting a disregard for nuclear safety by Russian soldiers.

The IAEA said that the remote transfer of data from the Chernobyl plant to its headquarters in Vienna is slowly being restored.