Nearly 100 per cent of voters in four sham referendums in Russian-held regions of Ukraine supported joining Russia, Moscow declared on Tuesday.
After five days of voting, Russian-installed officials claimed over 96 per cent of residents had backed becoming part of Russia, according to their initial counts.
Vladimir Putin, Russia’s president, is now expected to announce the accession of the occupied areas of Donetsk, Luhansk, Zaporizhzhia and Kherson into the Russian Federation within days, according to British intelligence.
Ahead of their expected annexation, Dmitry Medvedev, a close ally of Mr Putin, issued a fresh nuclear warning to Kyiv and the West over attempts to reclaim the territories, which make up some 15 per cent of Ukraine.
Russian officials, flanked by armed guards, took ballot boxes door-to-door in order to force residents to vote, threatening to massacre their families if they didn't.
Ukraine and the West have branded the referendums an illegitimate attempt to create a legal veneer for Russia to cement control over the four regions.
Analysts believe Mr Putin will use annexation to portray any Ukrainian attempt to liberate the areas as a direct attack on Russia.
In an attempt to prevent Western governments from assisting Kyiv, the Russian president last week said he was prepared to use nuclear weapons to defend his country's "territorial integrity".
Writing on the Telegram messaging app on Tuesday, Mr Medvedev, deputy chairman of Russia's security council, said: "I believe that NATO would not directly interfere in the conflict even in this scenario.
"The demagogues across the ocean and in Europe are not going to die in a nuclear apocalypse."
Ukrainian soldiers close in on eastern city
Meanwhile, Ukraine's armed forces edged closer to the eastern city of Lyman, capturing several surrounding villages in the Donbas.
Pro-Russian military bloggers warned that Kyiv's forces could soon cut off the only safe supply routes into the city, a strategic hub for Russian troops.
Rybar, a widely read pro-Kremlin military Telegram channel, said the Russian line of communication was "under threat of being blocked, as Ukrainian troops attempt to encircle Lyman from the west.
Others said it was possible that Russian forces would surrender the town without Ukraine launching a direct assault on it.