Nuclear power plant workers being held hostage by Russian forces are allegedly surviving on just two hours sleep and one meal a day as they try to keep the facilities working.
Russian forces seized Ukraine's Zaporizhzhia nuclear power plant on Friday and have now placed staff running the facility under their command, according to the U.N. nuclear watchdog.
The International Atomic Energy Agency said it was "extremely concerned" about developments at Zaporizhzhia, Europe's largest nuclear power plant.
Officials are struggling to contact the hostages after Russian forces blocked vital channels of communication.
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"Ukraine reports that any action of plant management - including measures related to the technical operation of the six reactor units - requires prior approval by the Russian commander," the IAEA said in a statement.
"In a second serious development, Ukraine has reported that the Russian forces at the site have switched off some mobile networks and the internet so that reliable information from the site cannot be obtained through the normal channels of communication," it added.
Russian forces also seized the spent-fuel and radioactive waste facilities at Chernobyl, next to the now defunct power plant on February 24.
More than 200 people at the site, including technical staff and guards, have not left since the day before the invasion.
The UN agency has called for technical staff to be rotated out on safety grounds but the Ukrainian regulator is "facing problems communicating with personnel" at Chernobyl, said the IAEA, adding that communication was only possible via email.
Workers at Chernobyl are said to be "starving, exhausted and depressed" as they survive on just one meal of porridge a day and two hours sleep, reports the Daily Mail.
A source told the publication: "'With nowhere to sleep and no blankets, many are only sleeping for two to four hours on desks or wherever they can find a space.
"They are running out of food and are down to one meal of porridge a day. They are fed once every 24 hours, if there is enough they might get extra bread."
The site is usually run by a staff of 500 people with the hostages forced to work round-the-clock to keep the site of the world's worst nuclear disaster safe.
Ukrainian authorities said Russian forces had seized control of Zaporizhzhia - which houses six reactors - on Friday after setting the neighbouring training facility on fire.
Russia's defence ministry blamed the attack on Ukrainian saboteurs, calling it a "monstrous provocation".
The fire was put out and there was no damage to reactors or release of radioactive material but the incident raised concerns about the potentially catastrophic consequences should the conflict damage one of the country's four operating nuclear power plants.
IAEA chief Rafael Grossi said: "In order to be able to operate the plant safely and securely, management and staff must be allowed to carry out their vital duties in stable conditions without undue external interference or pressure."
