The head of Ukraine's atomic agency, Enerhoatom, has accused Russian occupation troops at the Zaporizhzhya nuclear power plant in war-torn southeastern Ukraine of torturing and killing some of the facility's Ukrainian staff and abducting around 200 of them.

Enerhoatom President Petro Kotyn told the German newspaper group Funke in statements published on September 8 that he has no idea where some of the abductees are.

The accusations come amid reports of fresh shelling around the six-reactor plant and a power outage in the surrounding town heightening international fears of a nuclear catastrophe.

Kotyn said the occupying troops are screening the plant's staff to determine their national loyalties.

He said abuses have made it very difficult for the 1,000 or so remaining employees to keep Europe's largest nuclear power plant running.

Some 11,000 people worked at the Zaporizhzhya plant before it fell under Russian control in the early weeks after Moscow launched its unprovoked invasion of Ukraine in late February.

The International Atomic Energy Agency (IAEA) reported this week that its recent inspection of Zaporizhzhya demonstrated an "untenable" situation there and "an urgent need for interim measures" to avoid a nuclear accident.

The IAEA, the UN's nuclear watchdog, warned that staff shortages and stress levels risked operational failures.

It also said its 14 UN inspectors hadn't been granted access by the Russian occupiers to all areas of the nuclear plant.

Two IAEA experts remained behind at Zaporizhzhya for monitoring and safety reasons.

The agency said on September 7 that "renewed shelling has damaged a back-up power line between Ukraine’s Zaporizhzhya Nuclear Power Plant (ZNPP) and a nearby thermal power station, further underlining significant nuclear safety risks at the facility."

The governor of the Dnipropetrovsk region and the mayor of the town of Enerhodar in which the Zaporizhzhya plant lies both accused Russian forces of renewed shelling on September 7 that knocked out power nearby.

Governor Valentyn Reznichenko said there were "fires, blackouts, and other things at the [plant] that force us to prepare the local population for the consequences of the nuclear danger."

Authorities have reportedly distributed iodine pills in recent days to help protect the local population in the event of a radiation leak.

In Enerhodar, pre-occupation Mayor Dmytro Orlov said local services were impossible for workers to deliver after a second day of Russian shelling that "reduces their work to zero."

He said via Telegram on September 7 that "it is now impossible to predict the timing of the restoration of electricity supply."

The Ukrainian and Russian sides have each blamed the other for bombing and other dangerous activities around the plant.

Nuclear experts have warned of a possible Chernobyl- or Fukushima-style meltdown if the reactors are starved of power supplies.

Russian President Vladimir Putin on September 7 continued to blame Ukrainians for creating "threats to nuclear security" and shelling at and around the plant -- a charge that Kyiv has rejected while accusing Russian forces of risky bombing and "nuclear terrorism."

The IAEA has urged Russia and Ukraine to establish a “nuclear safety and security protection zone” around the plant and said shelling at the site and its vicinity should stop immediately.

Kyiv has demanded that, too, as well as a return of the facility to Ukrainian control.

With reporting by AP and Reuters