UN nuclear watchdog chief Rafael Grossi will visit the Russian-held Zaporizhzhia nuclear power plant in Ukraine this week to assess the serious situation there, he announced on Saturday.

Grossi is pressing for a security zone to be erected around what is Europe’s largest nuclear power plant, with six reactors, which has come under repeated shelling over the past months.

It will be his second visit. Last September he went there and established a permanent presence of IAEA experts.

Russian troops occupied the facility early in their invasion of Ukraine and it remains near the front line. Both sides blame each other for the shelling the plant has endured since Russian forces swept into during the first days of the war.

“The situation at the Zaporizhzhia nuclear power plant is still precarious,” Grossi said in the statement, saying he wanted “to assess first-hand the serious nuclear safety and security situation at the facility”.

Earlier this month he appealed for a protection zone around the plant to be set up, saying he was “astonished by the complacency” around the issue.

On March 9, Russian rocket attacks severed the plant’s access to outside power, jeopardizing safety and coolant systems necessary to keep the facility’s reactors from overheating and melting down.

Though power was restored, it was only one of several times that the plant has been cut off from the grid since fighting in the Zaporizhzhia region intensified last summer.

“Each time we are rolling a dice,” Grossi told the IAEA’s 35-nation Board of Governors at that time. “And if we allow this to continue time after time then one day our luck will run out.”

Grossi has labored unsuccessfully for months with officials in Moscow and Kyiv to broker an agreement that would see the Zaporizhzhia plant declared off limits to military incursions.

At present, the plant’s six reactors are offline and in various stages of shutdown, which should make a major radiation accident less likely. But even while offline, the reactors still require cooling systems to prevent the uranium fuel within them from overheating.

The plant accounted for around 20% of Ukraine’s national power generation before the invasion, but has not produced any electricity since September when the last of its six reactors was taken offline.