Russian President Vladimir Putin ordered the government Wednesday "to take into federal ownership the facilities of the Zaporizhzhia nuclear power plant and other property necessary for the implementation of its activities."
In a separate decree, he ordered the government to publish a new text of the Russian Constitution with amendments on the number of regions.
The Kremlin website said the necessity arose because of the "accession of four new regions to Russia."
Earlier Wednesday, the president approved the ratification of the "admission" of Ukraine's Donetsk, Luhansk, Zaporizhzhia and Kherson regions into the Russian Federation.
On Tuesday, the Russian parliament ratified agreements on annexing the Ukrainian regions.
Putin signed agreements last Friday with separatist authorities of the breakaway Ukrainian regions on joining Russia, following "referendums" held Sept. 23 - 27.
The vote came more than seven months into Russia's war against Ukraine that began Feb. 24.
The "referendums" have been condemned by the international community, with European nations and the US calling them a "sham" and underlining that they would not be recognized.
Ukrainian President Volodymyr Zelenskyy said Putin's decision to annex the four regions is invalid and has no legal consequences.