Russia will annex four occupied regions of Ukraine at a ceremony at the Kremlin on Friday, Moscow said, after President Vladimir Putin threatened he could use nuclear weapons to defend the territories.
The Russian leader is expected to deliver a major speech at the event, following referendums held last week in which four Ukrainian regions voted in a landslide to join Russia, but which were dismissed as a sham by the West.
Russia recognised the independence of the two other regions it is preparing to annex -- Donetsk and Lugansk -- at the end of February.
"I order the recognition of the state sovereignty and independence" of the regions of Zaporizhzhia and Kherson, located in southern Ukraine, Putin said in the decrees.
Putin's nuclear threats have not deterred a sweeping Ukrainian counter-offensive, which has been pushing back Russian troops in the east and is on the doorstep of the Donetsk town of Lyman, which Moscow's forces pummelled for weeks before capturing it this summer.
Putin has blamed the conflict in Ukraine on the West and said simmering conflicts in the former Soviet Union were the result of its collapse.
The rhetoric built on his now-famous phrase that the fall of the USSR was a tragedy, and he has recently suggested Moscow should extend again its influence over the former Soviet region.
The Kremlin-installed leaders of the four regions that pleaded to Putin for annexation this week were gathered in the Russian capital on Thursday, ahead of the ceremony.
Their nearly simultaneous requests came after they claimed residents had unanimously backed the move in hastily organised referendums that were dismissed by Kyiv and the West as illegal, fraudulent and void.
Ukraine said the only appropriate response from the West was to hit Russia with more sanctions and to supply Ukrainian forces with more weapons so they could keep reclaiming territory.
US President Joe Biden said Thursday that "the United States will never, never, never" recognise Russia's claims on Ukraine's sovereign territory.
UN Secretary-General Antonio Guterres also rejected the annexation plans, condemning them as "a dangerous escalation".
"It must not be accepted," he said.
The UN Security Council will vote at 1900 GMT on Friday on a resolution condemning the referendums, according to France, the council's current president.
But the resolution -- drafted by the United States and Albania and whose exact contents are not yet public -- has no chance of passing due to Moscow's veto power, though it can be presented to the General Assembly after the vote.
Ukraine's President Volodymyr Zelensky called an "urgent" meeting of his national security council for Friday, his spokesman said, after the Kremlin announced the timing of the annexation ceremony.
The four territories create a crucial land corridor between Russia and the Crimean peninsula, annexed by Moscow in 2014.
Together, all five make up around 20 percent of Ukraine, whose forces in recent weeks have been clawing back ground.
In the south, Ukrainian forces have been wresting back territory near Kherson, and residents of recently recaptured villages described the months spent under Russian occupation.
"They robbed and humiliated us," 72-year-old Maria Syzhuk said in the village of Vysokopillya, over the dull thuds of artillery from both sides -- mostly in the distance, but sometimes a little closer.
Ukrainian troops in particular have been progressing in the eastern Kharkiv region and recapturing territory in Donetsk. Military observers say Kyiv's forces are close to capturing Lyman.
- 'I don't want to kill people' -
Moscow's forces are striking back along the entire frontline and officials in Kyiv said Thursday that Russian bombardment had killed three in the Dnipropetrovsk region, killed five in Donetsk and wounded seven in the Kharkiv region.
Along with threats to use nuclear weapons, Putin announced a mobilisation of hundreds of thousands of Russians to bolster Moscow's army in Ukraine, sparking demonstrations and an exodus of men abroad.
Putin on Thursday called for mistakes with the draft to be "corrected", as discontent grows over the often chaotic conscription push.
Finland's Vaalimaa crossing has been flooded with new arrivals recently. Helsinki announced on Thursday it would close its border from midnight to Russians holding European tourism visas for the Schengen zone.
"I just made it through, I don't know how the others will get through," Andrei Stepanov, a 49-year-old Russian, told AFP.
On a bright morning in Mongolia's capital Ulaanbaatar, a young Russian fleeing Moscow's first military call-up since World War II had a stark answer for why he had left: "I don't want to kill people."
"It was very difficult to leave everything behind -- home, motherland, my relatives -- but it's better than killing people," the man in his 20s told AFP, speaking on condition of anonymity.
Belarus was preparing to host 20,000 Russian soldiers, converting warehouses, hangars and abandoned farms into military accommodations, Ukraine's ministry of defence said on Thursday.
To bolster Ukraine, the United States pledged more money on Thursday, with the Senate approving $12 billion in new economic and military aid as part of a stopgap budget extension.
The European Commission has proposed fresh sanctions targeting Russian exports worth seven billion euros, an oil price cap, an expanded travel blacklist and asset freezes.