Authorities in separatist- and Russia-occupied regions of Ukraine on Tuesday said they will stage referendums on formally joining Russia in a matter of days.

The announcement comes as Moscow’s forces face continued setbacks in their nearly seven-month war against Kyiv, leading to speculation that the Kremlin could announce a wider mobilization to shore up its military.

The Donetsk People’s Republic (DNR) and the neighboring Luhansk People’s Republic (LNR) will both hold their referendums on Sept. 23-27, officials there said.

DNR leader Denis Pushilin said that a vote on joining Russia was overdue.

“I think that people have long been waiting for a referendum here and it will probably be a political move that will help ensure the safety of civilians,” Russian news agencies quoted him as telling state television. 

Moscow-installed officials in the occupied Kherson region and partially occupied Zaporizhzhia region soon followed suit, announcing their own referendums to be held on the same dates as the DNR and LNR.

“We have set a course for reunification, a return to Russia. And we will not turn away from it,” Kherson’s Moscow-appointed leader Vladimir Saldo said in a video message.

The Moscow stock exchange was down by more than 10% at one point following the announcements, the Kommersant business daily reported.

Earlier Tuesday, former Russian President Dmitry Medvedev called the possible referendums in the Donetsk and Luhansk regions “essential,” saying they would allow Moscow to utilize its full military capability in the region.

“Encroachment onto the territory of Russia is a crime which allows you to use all self-defense forces,” Medvedev, who is now the deputy head of Russia’s Security Council, said in a post on the Telegram messaging app.

Russia’s Foreign Minister Sergei Lavrov also backed the referendums.

“The current situation proves that they [people from the occupied regions] want to be masters of their own destiny,” Lavrov said.

Russian State Duma speaker Vyacheslav Volodin said Moscow would support the separatist republics if their residents voted in favor of joining Russia.

“Everything that is happening today (calls to hold referendums) is an absolutely unequivocal ultimatum from Russia to Ukraine and the West,” said Tatiana Stanovaya, a nonresident scholar at the Carnegie Endowment for International Peace.

“To guarantee ‘victory,’ Putin is ready to hold referendums immediately to get the right (as he thinks) to use nuclear weapons to defend Russian territory,” Stanovaya said in a Telegram post on Tuesday, adding that Putin could use the possible annexation “to threaten the use of nuclear weapons to defend Russian territory.”

Large parts of the industrial Donbas area have been controlled by Moscow-backed separatists since 2014, after nationwide demonstrations ousted Ukraine’s Kremlin-friendly president.

Russia at the time annexed the Crimean peninsula from Ukraine with a vote that was criticized by Kyiv and the West, which imposed sanctions in response.

Both Kyiv and its allies in the West have likewise said they will not recognize the results of any new referendums in separatist- or Russia-controlled regions.

And Ukraine on Tuesday vowed to “eliminate” Russian threats against the war-torn country following the separatists’ referenda announcements.

“Ukraine will solve the Russian issue. The threat can be eliminated only by force,” said the Ukraine presidency’s chief of staff, Andriy Yermak.

AFP contributed reporting.