An adviser to Ukrainian President Volodymyr Zelenskyy warned Thursday that attempts to return those who have been forcibly deported to Russia will be another frontline battle.

"This is a difficult procedure that will require intermediary countries or international institutions that will allow us to bring people back. I’d like to note that this will also be a war," Mykhailo Podolyak said. "After the war, there will be a war to take our people back."

Marianna Vishegirskaya stands outside a maternity hospital that was damaged by shelling in Mariupol, Ukraine, Wednesday, March 9, 2022. (AP Photo/Mstyslav Chernov, File)

FILE - Marianna Vishegirskaya stands outside a maternity hospital that was damaged by shelling in Mariupol, Ukraine, Wednesday, March 9, 2022. (AP Photo/Mstyslav Chernov, File)

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Countless reports have circulated in the eight weeks since Russia’s invasion began that Ukrainian citizens have been transported to Russia against their will. 

Ukraine’s human rights ombudsman Lyudmyla Denisova – who is investigating allegations of human rights abuses – took to Telegram Thursday to report that a group of teenagers from Ukraine’s eastern Luhansk and Donetsk regions were forcibly deported to Russia after their parents had been killed in the war.

Denisova additionally reported last week that 400 Ukrainians, including 145 children, were being detained in a fenced camp near the Russian city of Penza which was previously a munitions dump for Soviet chemical bombs after World War II.

Mariupol city mayor Vadym Boychenko also sounded the alarm earlier this month that some 31,000 residents of the partially besieged city had been deported at gunpoint to Russian "filtration camps."

But the presidential adviser on Thursday suggested that figure could actually be much higher and claimed 100,000 Donetsk residents had been deported. 

A resident looks at a damaged apartment building in Mariupol, Ukraine, on Saturday.  (AP/Alexei Alexandrov)

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"They will not tell us objective information that, for example, of the 100,000 deported from Mariupol, Volnovakha and other regions of the Donetsk region, only five percent wanted to go to Russia, and the rest were forcibly deported there," he said in an address translated by the Ukrainian government. 

Podolyak claimed that Russia has a history of "resettling" citizens of nations it invades in an attempt to "separate them from their homeland."

The adviser warned Russia will claim these people voluntarily immigrated.

"In terms of propaganda, the Russians will lie to the whole world," he added. 

Podolyak said legally verified lists need to be drawn up to identify each individual who was deported to Russia.

Ukrainian servicemen ride atop an armoured fighting vehicle Tuesday as Russia's attack on Ukraine continues at an unknown location in Eastern Ukraine. (Press service of the Ukrainian Ground Forces/Handout via REUTERS)

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The adviser said it will need to be an international effort to safely return those who were deported by having representatives from international organizations meet with each individual.

"This is a whole legally sound procedure for us to take them back," he added.