Officials in four Moscow-occupied regions of Ukraine on Tuesday claimed victory in referendums for a merger with Russia amid international condemnation of sham ballots.
The local poll body in the southern Zaporizhzhia region said 93.11% of voters opted for Russian annexation after all ballots were counted.
It said however that this was a preliminary result.
In Kherson, also in the south, authorities said 87.05% of voters opted for Russian annexation after a vote count was completed.
In the eastern Lugansk region controlled by pro-Russia separatists, 98.42% opted for annexation by Russia, Russian news agencies said, citing local authorities.
"It is clear" that Lugansk will return to the Russian fold, Leonid Pasechnik, the leader of the self-proclaimed Lugansk People's Republic, said on Telegram.
In the Donetsk region in eastern Ukraine, the poll body said 99.23% of voters opted for Russian annexation after all ballots were counted, according to news agencies.
Denis Pushilin, the Kremlin-backed separatist leader in Donetsk, said: "We have all wanted this for a very long time", according to Russia's state-run news agency RIA Novosti.
He welcomed what he called the "colossal" result, saying: "We are reuniting with our great homeland, with great Russia."
The United Nations meanwhile said it was "committed" to Ukraine's "territorial integrity" within "recognised" borders.
Earlier, President Volodymyr Zelensky told the United Nations General Assembly that Ukraine will not be able to negotiate with Russia after Moscow held the annexation "referendums".
"Russia's recognition of the pseudo-referendums as 'normal', implementation of the so-called Crimean scenario, and yet another attempt to annex Ukrainian territory means that there is nothing to talk about with (the) current Russian president," he said in a video message.
"In front of the eyes of the whole world, Russia is conducting an outright farce called a 'referendum' on the occupied territory of Ukraine," he said.
"People are forced to fill out some papers for a TV picture under the muzzles of machine guns. The figures of the alleged results of the pseudo-referendum were drawn in advance," he said.
Mr Zelensky added that "threats to use nuclear weapons have become a constant narrative of Russian officials and propagandists".
He claimed the votes were "a farce" and they "cannot even be called an imitation of referendums".
"We will act to protect our people: both in the Kherson region, in the Zaporizhia region, in the Donbas, in the currently occupied areas of the Kharkiv region, and in the Crimea," Mr Zelensky said.
Vlaimir Putin said Russia would use any and all available means to defend its territory, implying that after the four regions were annexed Moscow could deploy strategic nuclear weapons to repulse Ukrainian attempts to retake the territory.
Pentagon spokesman Patrick Ryder said the United States was taking the threat "seriously" but had seen nothing to change its nuclear posture.
"Russia must know that the nuclear war cannot be won and must never be fought," said NATO chief Jens Stoltenberg.
The four Russian-occupied regions of Ukraine - Donetsk and Luhansk in the east and Kherson and Zaporizhzhia in the south - announced that they would hold the elections just days before voting began last Friday.
Together, they form a crucial land connection for the Kremlin between Russia and the Crimean peninsula, which Moscow annexed in 2014 and is otherwise only connected to the mainland by bridge.
US Secretary of State Antony Blinken vowed that the West would never recognise Russian annexations of the territories, threatening Moscow with "additional swift and severe costs" for its "diabolical scheme".
French Foreign Minister Catherine Colonna, in Kyiv for a surprise visit to meet Ukrainian President Volodymyr Zelensky, called the polls a "masquerade" that would trigger further Western sanctions.
She also said moves were underway for a resolution against Russia at the current UN General Assembly in New York.
Even Russia's closest ally since the start of the invasion, China, said after the votes were announced last week that Russia should respect territorial integrity in the war.
The so-called referendums follow a pattern that Moscow utilised in Crimea after nationwide street demonstrations saw Ukraine's Kremlin-friendly president ousted.
Like then, the outcome of the ballot was viewed by observers as a foregone conclusion. Election officials brought ballot boxes door-to-door in many cases accompanied by armed Russian forces.
Lawmakers are expected to vote hastily to annex the territories after the results are announced and Russian news agencies have said Mr Putin could sign legislation formalising the land grab this week.
Ukrainian forces meanwhile have pursued their counter-offensive in the east.
The governor of the eastern Kharkiv region announced its forces had recaptured Kupiansk-Vuzlovyi, "one of the largest logistical and railway junctions" in the region, and not privy to this week's vote.
Polling stations were open in Crimea for people who fled fighting after the Russian invasion in February.
"With my voice I want to try to make a small contribution to stopping the war," 63-year-old Galina Korsakova from Donetsk told AFP.
"I really want to go home," she said.
Along with threats to use nuclear weapons, Mr Putin announced a mobilisation of hundreds of thousands of Russian men to bolster Moscow's army in Ukraine, sparking demonstrations and an exodus of men abroad.
The United Nations voiced alarm at credible reports of nearly 2,400 arrests in less than a week during nationwide protests in dozens of cities against the draft order.
The European Union's border agency Frontex said the number of Russians entering the bloc last week was up 30% compared with the preceding week.
Ex-Soviet Georgia, invaded by Russia in 2008, said the numbers of Russians crossing its borders had increased to around 10,000 people daily since Mr Putin's announcement.
Kazakhstan, a Central Asian country on Russia's southern border, said nearly 100,000 people had entered the country since the 21st of September.