DNIPRO, Ukraine—United Nations inspectors visited the Russian-controlled Zaporizhzhia nuclear-power plant on Thursday after crossing the front line between Ukrainian and Russian forces despite intense shelling in the area that the two sides blamed on each other.
The director general of the U.N.’s International Atomic Energy Agency, Rafael Grossi, said late on Thursday that he was finishing his first visit to the plant and that the IAEA “is here to stay and will maintain a continued presence” at the plant. Ukraine’s nuclear-energy regulator, Energoatom, said five members of the team had remained.
Mikhail Ulyanov, Russia’s permanent representative to the IAEA, said the rest of the delegation was heading back to Vienna.
The visit is the outcome of months of wrangling over access to Europe’s largest nuclear-power plant, which has been largely closed off from the world since Russian forces seized it in the early days of their invasion of Ukraine. Heavy fighting near the plant has raised international concerns of a potential nuclear accident.
Footage published on social media by a Russian official showed Mr. Grossi shaking hands with officials outside the plant in the town of Enerhodar following a 75-mile journey from the Ukrainian city of Zaporizhzhia.
Shelling in the vicinity of the plant hours before the 14-member team’s departure had threatened to disrupt the visit, but Mr. Grossi said it would go ahead despite the risks being “very, very high.”
Yevhen Balitsky, the Russian-installed head of the administration in occupied parts of the Zaporizhzhia region, said the IAEA inspection would continue on Friday and potentially last longer.
Negotiations between the IAEA, Russia and Ukraine over access to the facility have taken on urgency in recent weeks as fighting around the plant has escalated. Ukrainian workers have continued to operate the facility, effectively at gunpoint, according to Ukrainian officials.
In a sign of how important the plant is to Kyiv, Ukrainian troops tried to retake it early Thursday. Russia’s Ministry of Defense said it had thwarted an attempt by Ukrainian “saboteurs” who crossed the Dnipro River in seven boats, landing on the bank of the Kakhovka reservoir.
Ukraine accused Russian forces of shelling the corridor through which the IAEA delegation was set to travel on Thursday, as well as Enerhodar.
“The city has been relentlessly pummeled by mortars since five in the morning,” said Dmytro Orlov, Enerhodar’s exiled mayor. “Machine gun salvos can be heard.”
Energoatom said shelling in the vicinity of the plant had shut down one of its operating power units and damaged a backup power-supply line.
Russia’s Defense Ministry said four shells fired by Ukrainian forces had landed about 400 meters from one of the plant’s power units, accusing Ukraine of seeking to disrupt the IAEA’s mission.
Russian Foreign Ministry spokeswoman Maria Zakharova said the inspection would “open the eyes” of the international community to the fact the threat to the nuclear plant comes from Kyiv, not Moscow. “The moment of truth is inexorably approaching,” she said.
Kyiv and Moscow have blamed each other for previous strikes that damaged the plant’s laboratory and chemical facilities. The facility was temporarily disconnected from Ukraine’s power grid last month as a result of fires that damaged cables.
Ukrainian officials say Russia aims to pressure the international community into forcing Kyiv to the negotiating table by raising the specter of a nuclear catastrophe.
Russia has stationed military equipment around the plant, Ukrainian officials say, using it as a shield for attacks against Ukrainian forces positioned on the opposite bank of the river.
Russian Foreign Minister Sergei Lavrov said Moscow was doing everything it could to ensure the plant continued to function safely “and that the mission has the opportunity to carry out all its plans.”
Talking to students and faculty at Moscow State Institute of International Relations on Thursday, he said Russia had wanted the IAEA team to arrive much sooner but that the plan was scuttled by Ukrainian shelling in the territory around the nuclear plant.
The IAEA team arrived in Ukraine late Monday, but plans to visit the plant were complicated by the launch of Ukraine’s new southern offensive and final questions over the security and parameters of the inspection, according to Ukrainian officials.
The Ukrainian offensive is aimed at dislodging Russian forces from a swath of territory in the south of the country.
Kyiv is seeking to show its Western backers—and its own people—that its military can take on Moscow’s army and win.
Ukrainian officials have said little publicly about the offensive, citing the need for secrecy in military operations, but soldiers who took part in fighting said they had retaken ground.
An assessment by the Pentagon, given at a briefing by its spokesman Wednesday, appeared to support the soldiers’ cautious optimism.
The front lines between Russian and Ukrainian troops have moved little in recent weeks, with both sides struggling to make meaningful gains after six months of fighting that have depleted manpower.
—Evan Gershkovich, Katia Rudeshko and Ann M. Simmons contributed to this article.
Write to Isabel Coles at isabel.coles@wsj.com
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