The European Union summoned Russia's envoy to the bloc to condemn and reject Moscow's "illegal annexation" of the Donetsk, Kherson, Luhansk and Zaporizhzhia regions of Ukraine, the bloc's diplomatic service said on Tuesday.
Russia declared the annexations on Friday after holding what it called referendums in occupied areas of Ukraine. Western governments and Kyiv said the votes breached international law and were coercive and non-representative.
The EU said it urged Moscow to reverse its "unlawful act" and unconditionally withdraw all its troops from the entire territory of Ukraine during Monday's meeting with Russia's charge d'affaires, Kirill Logvinov.
"The EU does not, and will never, recognise this illegal annexation by Russia," the bloc said in a statement. "These decisions by Russia are null and void and cannot produce any legal effect whatsoever."
The upper house of Russia's parliament voted on Tuesday to approve the incorporation of the four Ukrainian regions, even though Moscow does not have full control over any of them.
Its forces only control about 60% of the Donetsk region and 70% of Zaporizhzhia, while recent Ukrainian advances have also pushed the frontlines back into Luhansk, a region over which Russian forces claimed full control in July.
Moscow has proclaimed the annexation a "homecoming" of territories that were once part of the Russian empire, while Ukraine has vowed to recapture all the occupied lands.
Russian President Vladimir Putin, who has pledged to defend his "homeland and values", has accused the United States and its allies of waging a "hybrid war" against Russia and the separatist administrations it backed in eastern Ukraine.
(Reporting by Sabine Siebold; Editing by Charlotte Van Campenhout and Clarence Fernandez)