Ukrainian President Volodymyr Zelenskyy signed a decree on Tuesday that declares Russia's annexation of parts of Ukraine null and void.
Russian President Vladimir Putin's decision to annex Donetsk, Luhansk, Kherson and Zaporizhzhia regions, especially Crimea since 2014, is invalid, according to the decree.
They have no legal consequences, it added.
Zelenskyy also signed a decree earlier that said there will be no negotiations with Putin.
The latest move by Kyiv came after 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.
Separately, Zelenskyy had a tepephone call with Indian Prime Minister Narendra Modi. Zelenskyy emphasized the importance of strengthening the Ukrainian-Indian partnership against the backdrop of Russian "aggression" against Ukraine.
He noted that Ukraine will not conduct negotiations with Putin and said Ukraine has always been committed to peaceful settlement through dialogue.
Zelenskyy thanked Modi for India's support of Ukraine's sovereignty and territorial integrity and he emphasized the importance of the Indian leader's recent statement that now is not the time for war.
*Writing by Gozde Bayar
