"Every Russian soldier will bring a piece of Chernobyl home. Dead or alive," the minister added.
The head of the International Atomic Energy Agency, Rafael Grossi, later said "an increase in the levels" of radiation had been recorded at Chernobyl but insisted the matter was under control.
"The situation is not one that could be judged as posing a great danger to the environment and to people at the moment we were taking these measures," he added.
Shelestiy was unable to confirm details about alleged Russian misconduct at Chernobyl, where he was mostly forced to remain at his workstation and had little interaction with their troops.
'WORRIED, NERVOUS'
Amid the uncertainty, Shelestiy said he tried to console his team, whose families in the nearby town of Slavutych had been largely surrounded by Russian forces.
Back in Slavutych, mayor Yuriy Fomichev walked a fine line, managing relations with Russian forces, helping smuggle supplies into the besieged community and comforting the families of the captive workers.
"I had to calm them down and explain that it was necessary to be patient," said Fomichev.
Built in the aftermath of the Chernobyl accident as a settlement for evacuated families who had been living near the plant in 1986, Slavutych was one of the last purpose-made towns constructed from scratch during the final days of the Soviet Union.
For many of its residents, seeing chaos engulf Chernobyl again was an unwelcome case of deja-vu.
"We were worried, nervous," said Tamara Shyrobokova, 75, a former Chernobyl employee who was resettled in Slavutych following the meltdown.
"I was literally shocked by the fact that Russia attacked Ukraine. No-one could ever imagine this," she added.