Moscow said on Thursday it had issued more than 80,000 Russian passports to residents of four Ukrainian territories since President Vladimir Putin claimed to have annexed the regions last month.
"Since the addition ... of the four regions into the Russian Federation, and in accordance with the legislation, more than 80,000 people received passports as citizens of the Russian Federation," Valentina Kazakova, a migration official with the interior ministry, said in remarks carried by Russian news agencies.
In September, Russia held so called referendums in four regions of Ukraine -- Donetsk, Lugansk, Zaporizhzhia and Kherson -- and said residents had voted in favour of becoming subjects of Russia.
Putin formally annexed the territories at a ceremony in the Kremlin in early October, even though his forces have never had full control over them.
The United Nations condemned the "attempted illegal annexation" of Ukrainian land and urged the international community "not to recognize any changes announced by Russia to borders".
Russia has since lost swathes of territory that it controlled in Ukraine.
In November, Moscow pulled troops back from Kherson, the main city in the region of the same name and the only regional capital that Russia had captured in the Ukraine offensive.
Since the start of the military campaign in February, the Kremlin has made it easier for Ukrainians to obtain Russian nationality and allowed Ukrainian passport holders to live and work in Russia indefinitely and without a work permit.