The United Nations nuclear watchdog chief Rafael Grossi visited Ukraine on Tuesday unannounced to start providing assistance including experts and equipment aimed at keeping nuclear facilities there safe in the midst of war, apparently without Russia’s blessing.

Grossi’s visit comes as seasonal wildfires are ripping unchecked through the irradiated area surrounding Chernobyl, the defunct nuclear power plant that was seized by Russian troops on February 24. Ukrainian officials have said the blazes within the 2,600 square kilometer exclusion zone around the disaster site could bear radiation aloft to surrounding territories and across borders.

Since Russia invaded Ukraine last month, Grossi has called on both countries to agree a framework to ensure nuclear facilities, including spent nuclear fuel storage facilities at Chernobyl and Europe’s biggest nuclear power plant at Zaporizhzhya, are kept safe and secure.

International Atomic Energy Agency chief Grossi has so far failed to obtain such an agreement or even a three-way meeting with Ukraine and Russia. He had hoped to convene one at Chernobyl, which like Zaporizhzhya continues to be held under Russian control. He met the Ukrainian and Russian foreign ministers separately in Turkey almost three weeks ago.

On Wednesday Grossi appeared to make some progress, posting on Twitter that he had met with Ukraine’s energy minister and the head of Energoatom, the state company that oversees the country’s nuclear industry.

He also visited the South Ukraine nuclear power plant, whose three reactors are thought to be in the crosshairs of advancing Russian troops.

“IAEA’s on-site presence will help prevent the danger of a nuclear accident that could have severe public health and environmental consequences in Ukraine and beyond,” Grossi wrote.

On Monday, Lyudmila Denisova, commissioner of the Verkhovna Rada of Ukraine for human rights said the wildfires around Chernobyl have led to an increased level of radioactive air pollution that could threaten neighboring European countries.

She attributed the fires to Russian combat in the region, saying 31 blazes have been recorded, and she called on the IAEA to send firefighters and equipment to help tackle them.

“Control and suppression of fires is impossible due to the capture of the exclusion zone by Russian troops,” Denisova wrote in a Facebook post Sunday. “As a result of combustion, radionuclides are released into the atmosphere, which are transported by wind over long distances.”

The IAEA’s Grossi has not yet commented on the blazes, but their presence contributed to fears of yet more mishaps as Ukraine’s nuclear infrastructure falls under Russian fire.

Since the Chernobyl plant fell into Russian hands, nearby combat has cut power to the site twice, jeopardizing cooling processes for 22,000 spent nuclear fuel rods stores on plant territory. Ventilation is also required to tamp down radiation levels below the New Safe Confinement, a giant steel dome that was installed over the sarcophagus of Chernobyl’s Unit Four reactor, which exploded in 1986.

Power has since been restored, but the IAEA has reported it no longer has access to data transmitted by radiation sensors at the site.

At the Zaporizhzhya plant, a March 4 rocket strike destroyed a training laboratory. Like Chernobyl, the Zaproizhzhya’s plant’s staff is now essentially hostage to invading Russian forces – a situation that worries the IAEA. Since then, the Russian military has detonated ordinance at the plant that remained unexploded during its attack. The IAEA said that both the reactors and radiation levels remained safe after that incident.

Russians have also twice shelled the site of a US funded research reactor and nuclear research facility in the northeastern city of Kharkiv. The reactor’s fuel had reportedly been withdrawn prior to the onset of war and the IAEA said chances for an uncontrolled chain reaction at the site are low.