The Russian-installed leaders of the four regions of southeastern Ukraine have visited Moscow to finalise plans for annexation.
Donetsk, Kherson, Luhansk, and Zaporizhzhia have all held "referendums" on joining Russia in the last week.
Kyiv and its international allies have slammed them as a sham.
According to Russian officials, the four regions -- which represent about 15% of Ukraine -- voted overwhelming to be incorporated into Russian territory.
The West has stated that it will never recognise the annexation, with videos on social media showing armed soldiers enforcing the vote door-to-door.
"I am in Moscow," Leonid Passetchnik, the Russian-installed head of the Lugansk region, told the Tass news agency on Thursday.
The separatist leaders will soon be received by Russian President Vladimir Putin to ratify their "official" requests for annexation on Friday.
Russia's state parliament in Moscow is then expected to vote on the matter in the next few days.
In a sign that the Kremlin intends to mark the occasion, some streets in the Russian capital around the famous Red Square will be closed on Friday. Giant video screens have been set up, with billboards proclaiming “Donetsk, Luhansk, Zaporizhzhia, Kherson – Russia!”
European Commission president Ursula von der Leyen has proposed a fresh round of sanctions on Russia designed “to make the Kremlin pay” for escalating the conflict in Ukraine with the "sham referendums".
The Swedish coastguard said on Thursday that it had discovered a fourth gas leak on the damaged Nord Stream pipelines.
Damage to the undersea gas pipelines in the Baltic Sea has sent plumes of natural gas into the water near the island of Bornholm, while also heightening security concerns.
The European Union suspects
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