The EU on Wednesday slammed "illegal" annexation votes Russia held in four occupied regions of Ukraine and their "falsified" results, the bloc's foreign policy chief Josep Borrell said, according to AFP.

"EU denounces holding of illegal 'referenda' and their falsified outcome," Borrell said on Twitter.

"This is another violation of Ukraine's sovereignty and territorial integrity, amidst systematic abuses of human rights," he said.

European Council President Charles Michel tweeted: "Sham referenda. Sham results. We recognize neither."

On Tuesday, NATO chief Jens Stoltenberg called the votes organized by Moscow in the occupied Ukrainian regions as "a blatant violation of international law" which have "no legitimacy".

Kremlin-installed authorities in those regions are already claiming the ballots had gone Russia's way.

Russian President Vladimir Putin is expected on Friday to declare those regions annexed parts of Russia, coming under its nuclear umbrella.