New York: Amid the biggest reported missile attack on Ukraine in weeks, the UN’s atomic energy agency, IAEA, said on Thursday that Zaporizhzhya nuclear power plant had to switch to backup generators once again, after losing all power.

This is the first time the site has lost all power since November 2022 – but the sixth time that all off-site power has been cut since the Russian invasion last February - IAEA Director General Rafael Grossi said, in a statement to agency directors.

The agency said late on Thursday that power had been restored after 11 tense hours of being completely disconnected.

The plant has been occupied by Russian forces since the first few days of the full-scale invasion last year, but IAEA experts are deployed there and Ukrainian civilians continue to operate the plant, under the watch of the Russian military.

On Wednesday while in Kyiv, UN Secretary-General António Guterres noted that the IAEA had been “fully mobilized” to try and preserve the safety and security of nuclear facilities throughout Ukraine and called for the full demilitarization of the entire area around Zhaporizhzhya.

‘Our luck will run out’

“Each time we are rolling a dice. And if we allow this to continue time after time then one day our luck will run out,” the IAEA chief warned.

He added that “there is enough diesel on site for 15 days” to supply the plant’s “essential” needs but that the situation at Europe’s largest nuclear power station remains critical.

In an appeal for action to resolve the conflict and guarantee the safety of Ukraine’s nuclear infrastructure, Mr. Grossi said that he was astonished “by the complacency” of the international community.

He said he would continue to urgently consult Ukrainian and Russian authorities to help avert a potential nuclear disaster, should the reactor lose power altogether.

Massive wave of Russian strikes

Meanwhile across many areas of Ukraine, Russia once again launched a “massive wave of strikes”, killing civilians in several regions, UN Deputy Spokesperson Farhan Haq, told journalists at UN Headquarters on Thursday.

Russian missiles also struck civilian infrastructure in many parts of Ukraine, including the capital, Kyiv.

“The strikes – the first of this type in more than a month – hit power infrastructure across the country. In Kyiv, nearly 40 per cent of the people have been left without heat, while 15 per cent of homes and businesses lost access to electricity, according to the authorities”, Mr. Haq reported.

In the city of Kharkiv, liberated from Russian control during an offensive last September, he said 1.4 million people now lacked heating, electricity and water.

“In Kherson, the local authorities and our partners on the ground tell us that at least three civilians were killed at a bus stop in the city centre, which was understood to be hit by a missile.”

Civilians killed far from the front

Civilians were also killed and injured in the far west of Ukraine, in Lviv, close to the border with Poland.

Houses and other infrastructure were damaged in Zaporizhzhya and other front-line regions, Mr. Haq said.

“As the Secretary-General stressed yesterday in Kyiv, the United Nations has stayed on the ground”, the Deputy Spokesperson added, “delivering desperately needed humanitarian aid to millions of people in Ukraine.”