KYIV, Ukraine — The U.N. atomic watchdog warned of a potential threat to nuclear safety from a spike in fighting near Europe’s largest nuclear power plant in Ukraine, whose forces continued pressing their counteroffensive Saturday.

The International Atomic Energy Agency said its experts deployed at the Russia-occupied Zaporizhzhia Nuclear Power Plant reported hearing numerous explosions over the past week, in a possible indication of increased military activity in the region.

There was no damage to the plant.

“I remain deeply concerned about the possible dangers facing the plant at this time of heightened military tension in the region,” IAEA Director General Rafael Mariano Grossi warned in a statement issued late Friday.

He noted that the IAEA team was informed that staff at the nuclear plant had been reduced temporarily to minimum levels due to concerns of more military activity in the area.

“Whatever happens in a conflict zone, wherever it may be, everybody would stand to lose from a nuclear accident, and I urge that all necessary precautions must be taken to avoid it happening,” Grossi said.

The IAEA has repeatedly expressed concern that the fighting could cause a potential radiation leak from the facility, which is one of the world’s 10 biggest nuclear power stations. The plant’s six reactors have been shut down for months, but it still needs power and qualified staff to operate cooling systems and other safety features.

As Ukrainian forces pressed to expand their gains after recently capturing the village of Robotyne in the Zaporizhzhia region, the U.K. Defense Ministry noted in its latest report that Russia has brought in reinforcements to stymie the Ukrainian advances.

“It is highly likely that Russia has redeployed forces from other areas of the front line to replace degraded units around Robotyne,” it said. “These redeployments are likely limiting Russia’s ability to carry out offensive operations of its own along other areas of the front line.”

The Kremlin also reaffirmed Saturday that Russia will not extend a landmark deal allowing Ukraine to export grain safely through the Black Sea until the West meets Moscow’s demands regarding its own agricultural exports.

Russia refused to extend the deal in July, complaining that a parallel agreement promising to remove obstacles to Russian exports of food and fertilizer hadn’t been honored. It said restrictions on shipping and insurance hampered its agricultural trade, though it has shipped record amounts of wheat since last year.

Ukraine and its Western allies have dismissed the Kremlin’s demands as a ploy to advance its own interests.

On Saturday, Japanese Foreign Minister Yoshimasa Hayashi arrived to Ukraine for an official visit and prayed at a church in the Kyiv suburb of Bucha, where some of the worst atrocities of Russia’s war occurred early during the invasion.

“I am grateful to Japan for remaining our key partner in Asia and supporting Ukraine,” Ukrainian President Volodymyr Zelenskyy said.

Speaking after talks with his Ukrainian counterpart, Hayashi pledged that “Japan will go hand in hand with Ukraine until peace returns to its beautiful land.”

Ukrainian Foreign Minister Dmytro Kuleba said that while Japan cannot provide Ukraine with lethal weapons, it has “already demonstrated that it can do many other important things to improve our security.”

Japan has given Ukraine more than $7 billion in assistance since the start of the full-scale invasion.