UPDATE 1-Russia calls U.N. idea to demilitarise Ukraine's Zaporizhzhia nuclear plant unacceptable

* This content was produced in Russia, where the law restricts coverage of Russian military operations in Ukraine. (Adds detail, quotes, context)

MOSCOW, Aug 18 (Reuters) - Russia's foreign ministry on Thursday rejected a proposal by U.N. Secretary General Antonio Guterres to demilitarise the area around the Russian-controlled Zaporizhzhia nuclear power plant in Ukraine, saying it would make the facility "more vulnerable".

The plant, Europe's largest of its kind, was captured by Russia in March, shortly after President Vladimir Putin ordered tens of thousands of troops into Ukraine in what he called a "special military operation".

Fears have grown in recent weeks over its safety and the risks of a possible Fukushima-style nuclear accident after Ukraine and Russia accused each other of shelling it.

Guterres, who is currently on a visit to Ukraine, earlier this month called for the withdrawal of military personnel and equipment from the power station and for "a safe perimeter of demilitarization."

Ivan Nechayev, a spokesman for the Russian foreign ministry, told a briefing on Thursday that the proposal was unacceptable to Moscow.

He accused Kyiv of organising what he called provocations and of being unable to control nationalist armed groups.

"That is the very reason that the proposals (on demilitarisation) are unacceptable," said Nechayev.

"Implementing them would make the power station even more vulnerable."

Russia says it keeps some troops at the plant to ensure its smooth running and security.

Kyiv accuses Russia of using the plant as a shield from which it shells Ukrainian targets. It also says Russia has shelled the plant; Moscow says Ukraine is the one shelling the facility.

Nechayev said a visit to the plant by the International Atomic Energy Agency (IAEA) could take place in the very near future and that experts could determine for themselves who had been shelling it.

Russia, which says it has no heavy weapons at the plant, earlier on Thursday accused Kyiv and the West of planning a "provocation" there on Friday. Kyiv dismissed the accusation as cynical and untrue. (Reporting by Reuters; Editing by Andrew Osborn)