Kremlin-installed officials in Ukraine’s regions controlled by Moscow’s forces vowed on Thursday to push ahead with polls on Russia’s annexation this week after world leaders condemned the polls and said the results were invalid.

Russian Foreign Minister Sergey Lavrov was due to defend what Ukraine’s allies are calling unlawful land grabs during a UN Security Council session convened by France over rights violations in Ukraine.

Four Russian-held regions of Ukraine — Donetsk and Lugansk in the east, and Kherson and Zaporizhia in the south — said they would hold voting for five days starting Friday.

Vladimir Saldo, the Moscow-installed head of Kherson who got caught up early in the Russian invasion, said the referendum will go ahead in his region despite criticism.

“The date is fixed. We have the green light. Voting starts tomorrow and nothing can stop it,” he told state-run Russian media.

“People have been waiting and demanding that this vote take place soon,” he added.

Western leaders meeting in New York this week unanimously condemned the ballots.

Speaking at the United Nations, US President Joe Biden accused Russian President Vladimir Putin of “shamelessly” violating the UN Charter with a war aimed at “erasing Ukraine’s right to exist as a state”.

The integration of the war-torn regions of Russia would represent a major escalation of the conflict, as Moscow could then attempt to claim it was defending its own territory against Ukrainian forces.

After the votes were announced by his proxies in Ukraine, Putin announced that Russia would call up about 300,000 reservists to bolster the war effort and warned that Moscow would use “all means” to protect its territory .

Former Russian leader Dmitry Medvedev said in a statement on social media that those tools included “strategic nuclear weapons.” He predicted that the constituencies “will integrate into Russia.”

For most observers, the results of the simultaneous votes are already a foregone conclusion and were rushed as Ukrainian forces made sweeping gains in a counter-offensive to retake the east.

The referenda are reminiscent of a similar vote in 2014, in which Ukraine’s Crimea peninsula was annexed by Russia. Western capitals said the vote was fraudulent and had imposed sanctions on Moscow.

Election officials in the Donetsk region, which has been partially controlled by Moscow-backed separatists since 2014, said voting would be door-to-door for the first few days. In the polling stations, however, that would only be possible on the last day, Tuesday.

Putin’s move this week to call up reservists for Ukraine sparked small protests across Russia that led to more than 1,300 people being arrested.

Flights from Russia to neighboring countries, mostly former Soviet republics, that allow Russians visa-free travel are almost fully booked and prices have skyrocketed, indicating an exodus of Russians wanting to avoid war.

Sergei, 44, looked lost and exhausted in the arrivals hall of the Armenian capital’s airport and said he fled Russia to avoid conscription.

“The situation in Russia would make anyone leave the country,” he told AFP news agency on condition of anonymity.

Dmitry, 45, said he flew to Armenia from one of Russia’s eastern regions with a small bag, leaving his wife and two children behind and “have no idea what I’m going to do here”.

“I don’t want to go to war. I don’t want to die in this senseless war,” he told AFP journalists.

However, Kremlin spokesman Dmitry Peskov on Thursday denied that eligible Russians were flooding airports and staying at the country’s borders.

“A lot of incorrect information has surfaced on this,” he said.

Russia’s Defense Ministry on Wednesday confirmed it had secured the release of 55 of its soldiers in the largest prisoner swap between Kyiv and Moscow since the conflict began.

In return, Ukraine has recovered 215 detained citizens, including soldiers who fought back against Russian forces besieging the Azovstal Steel Plant in Mariupol.

As part of the deal, Ukraine also handed over to Russia Viktor Medvedchuk, considered President Vladimir Putin’s key ally in Kyiv.

Medvedchuk, one of the richest people in Ukraine, was accused of high treason by Kyiv.