Senior Ukrainian officials say Russian forces will unleash large-scale missile strikes on Ukraine before the first anniversary on Friday of the start of the invasion.

Ukraine's presidential adviser Mykhailo Podolyak told local media on Saturday that he expects Russia to launch cruise and ballistic missiles against his country from Tuesday to Friday.

Ukraine's National Security and Defense Council Secretary Oleksiy Danilov also said Russia is preparing a massive missile attack against his country on Thursday and Friday.

Meanwhile, Ukraine's defense ministry said on Saturday that the Russian military launched missile attacks on civilian infrastructure in the western region of Khmelnytskyi. A nuclear power plant sits in the region.

But Russia's defense ministry said on Sunday that its forces fired sea-based cruise missiles at a military facility and an ammunition depot in Khmelnytskyi.

US think tank the Institute for the Study of War hinted that Russia may be trying to force emergency shutdowns of nuclear power plants in Ukraine.

The institute said Russian media "are advocating for Russia to carry out 'retaliatory strikes' that would systematically target electrical infrastructure supporting Ukrainian nuclear power plants."

Russian President Vladimir Putin is due to give his state of the nation address on Tuesday.

Kremlin spokesperson Dmitry Peskov told a state-run TV channel on Sunday that Russian lives are now centered around the subject of "the special military operation."

Peskov said people should expect the president to pay particular attention to the operation during his speech.