Fighting near Ukraine’s largest nuclear power plant has fueled fears of an international nuclear disaster, and world leaders are concerned.

Foreign ministers from the Group of Seven, an inter-governmental political forum of the world’s leading industrialized nations, demanded on Wednesday that Russia return control of the plant to Ukraine, according to Reuters.

Shortly after its February invasion of Ukraine, Russian troops took control of the Zaporizhzhia nuclear power plant in southern Ukraine, one of the world’s ten largest. Prior to the war, the plant supplied roughly half of Ukraine’s nuclear-generated electricity.

Ukrainian employees have been retained to ensure the plant’s continued operation. However, the conflict surrounding the plant has fueled fears of a nuclear disaster akin to the 1986 disaster at Chernobyl.

“We demand that Russia immediately return full control of the Zaporizhzhia nuclear power plant, as well as all nuclear facilities within Ukraine’s internationally recognized borders, to ensure their safe and secure operations,” the G7 foreign ministers said in a statement released in Germany on Wednesday, according to Reuters.

The International Atomic Energy Agency’s director-general, Rafael Mariano Grossi, told the Associated Press last week that the situation near the Zaporizhzhia plant is “completely out of control,” as he pleaded with Russia and Ukraine to allow inspectors to visit the site. According to Grossi, the supply chain for the plant’s equipment has been disrupted, and there have been reports of violence between Russian troops and Ukrainian staff members.

“What is at stake is extremely serious, grave, and dangerous,” Grossi stated.

In Russian-occupied southeastern Ukraine, guerrilla forces from Ukraine have blown up bridges and trains and killed pro-Moscow officials.

The resistance group Zhovta Strichka, or “Yellow Ribbon,” has been assisting the Ukrainian military and eroding Russian control in the area.

The guerrilla groups work with the Ukrainian military’s Special Operations Forces to select targets, plan ambushes, and establish a network of weapons caches and secret hideouts in Russian-occupied territory.

“Our goal is to make life unbearable for the Russian occupiers and use any means possible to derail their plans,” Andriy, a 32-year-old guerrilla movement coordinator in the southern Kherson region, told The Associated Press. He addressed the issue of not being fully identified.

Meanwhile, the Biden administration announced Monday that it was sending $1 billion in rockets, ammunition, and other material to Ukraine from Defense Department stockpiles as that country prepares for a potentially decisive counteroffensive in the south against Russia.

On Wednesday, the Ukrainian air force claimed that nine Russian warplanes were destroyed in a series of massive explosions at a Crimean air base. The explosions killed one person and injured 13 others.

Russia has denied that any aircraft were damaged, claiming that munitions at the air base caught fire and exploded. However, the explosions have fueled speculation that they were the result of a Ukrainian attack, though Ukrainian officials have refrained from publicly claiming responsibility.

The explosions also shattered windows, damaged nearby apartment buildings, and drove tourists away, and Russian officials attempted to minimize the damage.

For months, the IAEA has attempted in vain to send an inspection team to the plant.

Moscow has stated that it welcomes an IAEA visit to the plant, but it is unclear whether it is willing to assist in arranging such a visit.

Ukraine had previously objected to Grossi’s visit to the site as long as it was under Russian control, demanding that the Russian military withdraw.

However, Ukrainian officials appeared to be warming up to such a trip this week, with Ukraine’s ombudsman, Dmytro Lubinets, urging the United Nations and the International Atomic Energy Agency to send a delegation to help “completely demilitarize the territory” and provide security guarantees to plant employees.