Workers at Europe's biggest nuclear power plant fear a catastrophe is "waiting to happen" as Russia continues to occupy it.
Shells and rockets have it Zaporizhzhia - Ukraine's large nuclear power plant - since Russia gained control of it in March last year.
Engineers now fear one wrong move could trigger a disaster worse than Chernobyl.
Serhii, who works at the site, said: "The thing is, one month and a half ago there were two times fewer Russian troops on the power station.
"And now there are two times more which means they are definitely preparing for the counteroffensive.
"It would be much, much worse than Fukushima and worse than Chernobyl."
He told Sky News a power outage at Zaporizhzhia had he and many others worried about a radiation leak.
While five of the six reactors are now in cold shutdown, fears still loom that Vladimir Putin, 70, could decide to use the plant as a weapon.
Mykola, who also works at the plant in southeast Ukraine, compared the experience to being held as a hostage in his own workplace.
The nuclear technicians face intimidation from the occupying Russian soldiers and, as staffing is severely limited at the moment, some nuclear generators are not being maintained.
Before the war there were 11,000 staff at the plant and now there may be as few as 3,500, it is understood.
"The quality of the workers is lower because the qualified staff left. So generally the situation here is deteriorating," said Mykola.
Staff are concerned a disaster would leave thousands of square kilometres of land and sea of radioactive pollution, and a huge area of contamination.
Mykola continued: "I think the most important thing is not to get into their hands because it's unlikely you will get out and still be the human you were when you went in."
A top war chief last week said Ukraine is ready to launch its much-anticipated counteroffensive against Russian forces.
Oleksiy Danilov, one of the country's most senior security officials, highlighted the gravity of the situation and said that Ukraine’s government must avoid making mistakes in this historic opportunity.
And President Zelensky's most senior advisor, Mikhail Podolyak, told Italian radio station Rai1 last week: "It's an intense war on 1500km of border, but the actions have already started."
Ukrainian troops are known to be attacking around the flanks of Bakhmut in an attempt to surround the city.
Bakhmut was recently seized by Yevgeny Prigozhin's Wagner Group thugs, after a battle which saw many Wagner members running like "rats into a trap".
