Russian officials claimed that the occupied regions in Ukraine have approved Moscow's annexation in referenda held in the past few days.

More than 97% of voters from Ukraine's Luhansk, Donetsk, Kherson and Zaporizhzhya regions who cast ballots at polling stations within Russia voted in favor of joining the Russian Federation, state media in Russia reported on Tuesday.

Polling stations had been organized for displaced migrants from the four regions who were living in Russia.

A short time later, high number of votes in favor of joining Russia was also reported in Moscow from polling sites in the Russian-occupied territories themselves: According to initial data, more than 87% of voters in Kherson were in favor of joining Russia, and more than 92% in Zaporizhzhya.

Kyiv and countries around the world repeatedly denounced the five-day vote in areas under martial law as a "sham" and "illegitimate," claiming residents were coerced into voting out of fear for their safety and that the results were a foregone conclusion.

Ukrainian President Volodymyr Zelenskyy is set to address a special session of the U.N. Security Council later on Tuesday, sources told Deutsche Presse-Agentur (dpa) in New York.

The referendums raise the stakes in the seven-month war, with the West accusing Russia of looking to use the annexations as a justification for escalating its invasion.

As a next step, the Moscow-appointed occupation administrations are expected to formally apply to President Vladimir Putin to be incorporated into Russian territory. The Kremlin had indicated that this could happen quickly.

Putin had stressed before the start of the referendums that the territories would thereafter be completely under the protection of Russia, including its nuclear arsenal.

The chairperson of Russia's Federation Council, Valentina Matviyenko, said the upper house of parliament could decide next Tuesday whether to allow the occupied Ukrainian territories to join Russia.

Other media reports speculated that Putin could formally announce the annexation of the four territories in eastern and southern Ukraine as early as this Friday in a speech to both chambers of parliament.

Meanwhile, according to a newspaper report, Moscow plans the formation of a new federal "Crimean district," the Russian newspaper Vedomosti reported, citing sources in the Federation Council.

This district would include the Black Sea peninsula of Crimea, which was annexed in 2014, as well as the occupied parts of Kherson, Zaporizhzhya, Donetsk and Luhansk regions.

According to the report, the new head of administration is to be hardline nationalist Dmitry Rogozin, who was replaced as head of the space agency Roscosmos in July.

Kremlin spokesperson Dmitry Peskov said in response to questions from journalists that if decisions were made to create a new federal district, the Kremlin would inform them.

"We never announce such presidential decrees or personnel decisions," the Interfax agency quoted him as saying. However, he said the legal system and the executive branch are ready to admit new subjects to the federation after the votes in the territories.

On day 216 of the war, Ukrainian troops made further gains on the eastern bank of the Oskil river in the eastern region of Kharkiv.

The town of Pisky-Radkivski is once again under Ukrainian control, authorities announced on Monday night on Telegram alongside photos of destroyed Russian technology.

Prior to the Russian invasion on Feb. 24, the town had a population of about 2,000.

Earlier, Ukrainian headquarters had reported Russian shelling in Kupyansk-Vuslovyi about 40 kilometers (24.86 miles) to the north, indirectly confirming reports that the town had been retaken.

Kupyansk-Vuslovyi is an important railway junction on the left bank of the Oskil.

Following their expulsion from most of the province of Kharkiv in early September, Russian troops retreated behind the line of the Oskil and Siversky Donets rivers. They were unable to hold this line as Ukrainian troops reported successes in the Donetsk region, coming within a few kilometers of the Luhansk region.