Vladimir Putin has signed decrees recognizing two Ukrainian regions as independent territories.
The move lays the groundwork for Kherson and Zaporizhzhia to be annexed by Russia.
Putin is set to annex four Ukrainian territories this week after they held sham referendums.
Russian leader Vladimir Putin signed decrees on Thursday recognizing the independence of two Ukrainian regions - Kherson and Zaporizhzhia - and laying the groundwork for their expected annexation by Russia.
The decrees come ahead of Putin's expected announcement of Russia's annexation of the two territories, along with Donetsk and Luhansk, per Reuters.
The documents unilaterally declare both territories as being independent of Ukraine, a step required before they can be made a part of Russia.
Kremlin spokesman Dmitry Peskov said on Thursday that Russia would hold a signing ceremony in Moscow on Friday afternoon to declare the eastern Ukrainian regions as part of Russia, Reuters reported.
Per the outlet, Peskov said the ceremony would address "agreements on the accession of new territories into the Russian Federation."
The regions to be annexed make up around 15% of Ukraine's total territorial area, per Reuters.
Sham referendums that run counter to international law were recently held in the four Russian-occupied regions. The polls were organized by pro-Russian separatists and involved armed soldiers going house-to-house to collect votes, threatening Ukrainian families with violence if they refused to participate.
The illegal polls resembled a tactic used by Russia when it illegally annexed Crimea in 2014. At the time, election officials in the region announced an overwhelming vote in favor of unifying with Russia, which Moscow then used to justify its annexation.
According to the Associated Press, Russian troops currently have control of most of the Luhansk region and around two-thirds of the Donetsk region. The referendums may also be part of Russia's plan to force Ukraine to accept the annexation of these regions and to hold off a fierce Ukrainian counteroffensive in Kherson.
UN secretary general António Guterres has slammed Russia's actions.
"Any annexation of a State's territory by another State resulting from the threat or use of force is a violation of the Principles of the UN Charter and international law," Guterres said Thursday.
"The Russian Federation, as one of the five permanent members of the Security Council, shares a particular responsibility to respect the Charter. Any decision to proceed with the annexation of Donetsk, Luhansk, Kherson, and Zaporizhzhia regions of Ukraine would have no legal value and deserves to be condemned," he added.