Referendum voting in Russian-occupied territories of Ukraine is underway, a process Western and Ukrainian officials are rebuking as a sham by the Kremlin to legitimize Russian annexation of Ukrainian territory and make way for Russian President Vladimir Putin to justify nuclear strikes, reports Newsweek.

Referendums began Friday in the Ukrainian regions of Luhansk, Donetsk, Zaporizhzhia and Kherson, some of which are only partially controlled by Russia.

Ukrainian officials said people were banned from leaving some occupied areas until the four-day vote was over, armed groups were going into homes, and employees were threatened if they did not participate.

By incorporating the four areas, Moscow could portray attacks to retake them as an attack on Russia, potentially using that to justify a nuclear response.

"The Donbas [Donetsk and Luhansk] republics and other territories will be accepted into Russia," Dmitry Medvedev, the former Russian president and current deputy chairman of Russia's Security Council, in a Telegram post Thursday said any weapons in Moscow's arsenal could be used to defend territories incorporated into Russia from Ukraine.

"Russia has announced that not only mobilization capabilities, but also any Russian weapons, including strategic nuclear weapons and weapons based on new principles, could be used for such protection."

Putin on Wednesday accelerated his war effort in Ukraine, announcing a call-up of roughly 300,000 reservists to the military, while also threatening the West over its support for Ukraine.

"If the territorial integrity of our country is threatened, we will certainly use all the means at our disposal to protect Russia and our people," Putin said in a rare address to the nation. "This is not a bluff."

The Biden administration is prepared to impose "additional swift and severe economic costs on Russia along with our allies and partners in response to these actions if they move forward with annexation," White House press secretary Karine Jean-Pierre said during a daily news briefing.

"We have sent a loud message and our allies have as well about this illegitimate vote," she said, adding that the U.S. and its allies will never recognize land Russia annexes from Ukraine.

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