The vote on whether Russia should annex Ukraine’s Kremlin-controlled regions opened on Friday as the West denounced the referendum that has dramatically upped the stakes in Moscow’s seven-month invasion.

As the elections began, Ukrainian forces said they were retaking territory from Moscow-backed separatists and fighting for territory the Kremlin is trying to control.

The votes in four regions are the latest shock development in a savage war that UN investigators said has seen violence — such as executions and torture — amounting to war crimes.

Referendums in the eastern regions of Donetsk and Lugansk, and in the southern regions of Kherson and Zaporizhia were dismissed as “sham” by Kiev’s western allies.

And even diplomats from Russia’s closest ally since the start of the war, Beijing, have told Ukraine that “the sovereignty and territorial integrity of all countries must be respected.”

Authorities in Russian-controlled areas have been going door-to-door for four days to collect votes. The polling stations then open on Tuesday for residents to cast their votes on the final day of the election.

It was also possible to vote in the building in Moscow, which represents the breakaway region of Donetsk.

Leonid, a 59-year-old military official, told AFP he feels “happy”.

“Ultimately things are moving in the direction of restoring the Soviet Union. The referendum is a step in that direction,” he said.

Earlier this month, Ukrainian forces retook most of the northeastern Kharkiv region in a huge counteroffensive that saw Kyiv retake hundreds of settlements that had been under Russian control for months.

On Friday, Russia’s TASS news agency showed officials in Donetsk using loudspeakers to alert residents to the election and surrounded a local as he voted.

Denis Pushilin, a pro-Russian separatist leader in Donetsk region – part of the industrial Donbass region – said on Telegram that “Donbass is Russia”.

Kyiv said on Friday its forces had recaptured a village in the Donetsk region and recaptured positions south of the war-torn town of Bakhmut.

An integration of the four regions in Russia – a foregone conclusion for most observers – would mean a major escalation of the conflict.

“We cannot – we will not – allow (Russian President Vladimir) Putin to get away with it,” US Secretary of State Antony Blinken told the UN Security Council on Thursday, condemning the referenda as “bogus”.

The referendums commemorate Russia’s 2014 annexation of Ukraine’s Crimea. Western capitals claim that a similar vote at the time was fraudulent and sanctioned Moscow.

In Donetsk and Lugansk — which Putin had already recognized as independent before invading Ukraine in February — residents respond when they support “their republic’s entry into Russia,” TASS reported.

The ballots in Kherson and Zaporizhia ask: “Are you in favor of secession from Ukraine, the formation of an independent state by the region and its accession to the Russian Federation as a subject of the Russian Federation?”

Russian news agencies reported that voting began at 05:00 GMT on Friday, while TASS reported that paper ballots would be used to save time.

Ukrainian President Volodymyr Zelenskyy called the referendums a “farce”.

Chinese Foreign Minister Wang Yi, meanwhile, met his Ukrainian counterpart Dmytro Kuleba at the United Nations and told him that “the sovereignty and territorial integrity of all countries must be respected,” the ministry said in a statement in Beijing.

UN investigators on Friday said war crimes were being committed in the Ukraine conflict, citing Russian bombings of civilian areas, numerous executions, torture and appalling sexual violence.

Erik Mose, who led a team of investigators deployed in March, said they were “overwhelmed by the large number of executions”.

Putin said Moscow will use “all means” to protect its territory – what former Russian leader Dmitry Medvedev said on social media could include the use of “strategic nuclear weapons”.

Moscow began mandatory troop calls on Thursday after Putin called for about 300,000 reservists to step up the war effort.

But the men left Russia in droves before being tricked into joining, and flights to neighboring countries were booked in the coming days.

Some could not escape the summons.

Mikhail Suetin, 29, was among those arrested at a protest against mobilization in Moscow this week and received a summons to a recruitment office.

“To hear that ‘tomorrow you’re going to war’… that was a surprise,” Suetin, 29, who regularly joins opposition protests in Moscow, told AFP.