The director general of the International Atomic Energy Agency said Monday that a support and assistance mission to the embattled Zaporizhzhia nuclear power plant was expected to arrive later this week following more than a month of desperate diplomatic wrangling.

The UN nuclear watchdog has said for weeks that shelling at the enormous plant, which is Europe’s largest such facility, could lead to a radioactive accident or even a full-blown nuclear meltdown.  Russian troops have occupied the plant since early March, with Ukrainian staff continuing to tend its six reactors and radioactive waste stores essentially at gunpoint.

But the announcement of a UN mission to the plant raises hopes for progress even as the two sides accused one another of fresh rounds of shelling around the complex over the weekend.

“The day has come,” Rafael Grossi, the head of the IAEA, said in a tweet early Monday, announcing that a team was “on its way” after weeks of negotiations about getting nuclear inspectors access to the site near the conflict’s front lines.

“We must protect the safety and security of Ukraine’s and Europe’s biggest nuclear facility,” he said.

Grossi did not specify how the mission would reach the facility, which is in a region of southern Ukraine that has seen intense artillery strikes in recent weeks. But the announcement was welcomed by both the Ukrainian and Russia sides.

Dmytro Kuleba, Ukraine’s foreign minister, said on Monday that he expected the IAEA experts would conclude that Russia was putting “the entire world at risk of nuclear accident,” and repeated Ukraine’s calls for Moscow to withdraw its forces from the plant, according to the New York Times.

Kremlin spokesman Dmitry Peskov that Moscow considers the mission necessary, the Russian state news agency Tass reported.

He was quoted as saying that Russia will ensure the safety of the IAEA inspectors on the territory that it controls, but reiterated Moscow’s opposition to creating a demilitarized zone around the plant — saying that it’s up to the international community to pressure Kyiv to reduce tensions around the site.

Earlier, Mikhail Ulyanov, the Russian envoy to international organizations in Vienna, told the state news agency Ria Novosti that the mission consists of about 15 people and some of its members will stay behind at the plant “on a permanent basis.”

“We hope that the visit of the station by the IAEA mission will dispel numerous speculations about the unfavorable state of affairs” at the plant, he was quoted as saying.

With shelling in and around the plant on a near-daily basis and an exhausted and stressed team of Ukrainian engineers tasked with keeping it running, the arrival of international inspectors was widely seen as an urgent step.

Negotiations to allow access went on for weeks, with Moscow insisting that inspectors travel through Russian territory to access the plant. Ukraine objected because that would have underscored Russian control over the facility, which provides 20 percent of Ukraine’s electricity.

Last week, fighting in the area temporarily disconnected the plant from Ukraine’s power grid for the first time in its 40-year history, with President Volodymyr Zelensky warning that the incident left the world narrowly escaping a radiation catastrophe.

At the time of the outage, operators implemented emergency procedures to cool the reactor cores with pumps powered by diesel generators, but nearly all the Russia-occupied cities of southern Ukraine saw large-scale power outages before power lines line were repaired.

In subsequent days, fears of a possible radiation leak due to the fighting led Ukrainian officials to distribute potassium iodide, a drug that can protect against some forms of radiation poisoning, to people living within 55 kilometers of the plant.