Forced civilian deportations from Ukraine’s besieged port town of Mariupol to Russia are “unconscionable,” U.S. officials said Sunday after authorities in Kyiv and Mariupol’s mayor accused Moscow of transporting thousands of people against their will.

The claims are unverified so far but earlier this month Kyiv rejected an offer from Moscow to create “humanitarian corridors” allowing civilians to flee six heavily bombed Ukrainian cities when it emerged that Moscow expected the civilians to use the proposed safe routes to go to Russia or its ally, Belarus.

Only two of the corridors proposed by Russia would end up funneling civilians into safer Ukrainian-controlled territory. French president Emmanuel Macron accused Russia of “moral and political cynicism,” adding, “I do not know many Ukrainians who want to go to Russia.”

Ukraine’s leader, Volodymyr Zelenskyy, dismissed Moscow’s proposed routes for civilian evacuation to Russia as “completely immoral.”

The city council in Mariupol was the first to make the allegation about forced civilian deportations to Russia. The governor of the Donetsk region, Pavlo Kirilenko, also accused Moscow of having “forcibly deported more than 1,000 inhabitants of Mariupol.”

Kirilenko said deported civilians were being processed at Russian “filtration camps” where their mobile phones were checked and then their identity documents confiscated “Then they are sent to Russia,” he said on Facebook, adding “their fate on the other side is unknown.”

U.S. Ambassador to the United Nations Linda Thomas-Greenfield said Sunday: “I’ve only heard it. I can’t confirm it.” She added: “But I can say it is disturbing. It is unconscionable for Russia to force Ukrainian citizens into Russia and put them in what will basically be concentration and prisoner camps.”

According to some reports the deported civilians are being sent to remote Russian towns and given identity documents that indicate they can work where they are sent and are not allowed to relocate for two years.

The reports of the involuntary deportations have drawn scathing criticism from authoritative historians, who label them a distressing echo of the Soviet era when Communist autocrat Josef Stalin ordered deportations of entire nationalities, forced labor transfers and organized migrations in opposite directions to fill ethnically cleansed territories.

Stalin evicted 1.8 million kulaks from their homes and relocated them to labor camps and remote parts of Russia in 1930–31. A further estimated 1 million peasants and ethnic minorities were involuntarily relocated between 1932–39. Under Stalin’s rule 3.5 million ethnic minorities were forcibly relocated between 1930 to 1952.

In May 1944, over three days, nearly 200,000 Tatars, mostly women and children, were deported on cattle trains from Crimea and dispatched to Uzbekistan. Since the annexation of Crimea by Russia in 2014 Tatars still living on the peninsula have not been permitted to commemorate the event.

“If we’d paid attention to what Putin did to the Crimean Tatars after the 2014 annexation we’d hardly be surprised by his forced deportations in Mariupol today. Russian occupation forces are not merely committing war crimes in Ukraine, they’re committing crimes against humanity,” tweeted Jasmin Mujanović, the author of Hunger and Fury: The Crisis of Democracy in the Balkans.

“Plumbing yet more depths of evil, deportations from Mariupol to Russia, and according to Ukraine human rights spokesperson, deprived of passports and forced to work at specified Russian locations for at least 2 years — essentially deported slave labour,” tweeted Simon Schama, author of The Story of the Jews Volume Two: Belonging.”

Schama’s own family’s history included deportations and forced migrations which had among other relatives, his own parents passing through Turkey, Lithuania, Moldova and Romania.

“When Putin says that there is no Ukrainian nation and no Ukrainian State, he means that he intends to destroy the Ukrainian nation and the Ukrainian State. Everyone gets that, right?” tweeted Timothy Snyder, who specializes in the history of Central and Eastern Europe and the Holocaust.

Snyder was referencing Putin’s frequently repeated view that Ukrainians are basically Russians. The Russian leader has long pushed a narrative that Ukraine is part of Russia.

He famously declared to then-U.S. President George W. Bush in 2008: “You have to understand, George, that Ukraine is not even a country.” In 2014, after annexing Crimea and using armed proxies, later backed by the Russian military, to seize part of Ukraine’s Donbas region, Putin said: “Russians and Ukrainians are one people.”