Heavy fighting continued Friday near Europe's largest nuclear power plant in a Russian-controlled area of eastern Ukraine, a day after experts from the U.N.'s nuclear watchdog agency voiced concerns about structural damage to the sprawling Zaporizhzhia site.

Britain's Defense Ministry says shelling continued in the district where the Zaporizhzhia power plant sits. Ukrainian President Volodymyr Zelenskyy's office said Russian shelling damaged houses, gas pipelines and other infrastructure in the Nikopol region on the other bank of the Dnieper River.

The team of inspectors from the International Atomic Energy Agency, braving gunfire and artillery blasts along their route, crossed the frontlines to reach the Zaporizhzhia plant on Thursday in a mission to help safeguard the plant against catastrophe. Fighting Thursday prompted the shutdown of one reactor — underscoring the urgency of their task.

Read:UN inspectors arrive at Ukraine nuclear plant amid fighting

The 14-member delegation arrived in a convoy of SUVs and vans after months of negotiations to enable the experts to pass through the front lines. Speaking to reporters after leaving colleagues inside, IAEA director Rafael Grossi, said the agency was “not moving” from the plant from now on, and vowed Thursday a “continued presence” of agency experts.

Grossi said it was “obvious that the plant and the physical integrity of the plant has been violated several times” — but couldn't assess whether by chance or on purpose. “I will continue to be worried about the plant until we have a situation which is more stable,” he said.

Grossi said IAEA experts toured the entire site, including control rooms, emergency systems and diesel generators, and met with the plant’s staff.

The plant has been occupied by Russian forces but run by Ukrainian engineers since the early days of the 6-month war. Ukraine alleges Russia is using it as a shield to launch attacks, while Moscow accuses Ukraine of recklessly firing on the area.

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Before the IAEA team arrived, Energoatom, Ukraine’s state nuclear power company, said Russian mortar shelling had led to the shutdown of one of its reactors by its emergency protection system and had damaged a backup power supply line used for in-house needs.

IAEA announced plans for a news conference later Friday from its headquarters in Vienna to discuss the mission.

Energoatom on Friday accused Russian forces of “making every effort” to prevent the IAEA mission from getting to know the facts on the ground. On Thursday, Russian Foreign Ministry Sergey Lavrov said Russia was making sure that the plant was secure and safe, and that mission “accomplishes all of its plans there.”

Elsewhere in Ukraine on Friday, Zelenskyy's office said four people were killed and 10 injured over the last day in the eastern Donetsk region, a key hub of the Russian invasion, and reported rocket attacks on Sloviansk that destroyed a kindergarten. It said heavy fighting continues in two districts of the Kherson region to the south.