Ukrainian forces advanced dozens of miles into the Russian-occupied territories of Luhansk and Kherson on Monday, just days after Russian President Vladimir Putin claimed to annex the regions.

The Russian-installed chief of occupied Kherson told Russian state television that Ukrainian forces had seized control of the city of Dudchany, indicating an advance of roughly 25 miles in a single day, according to Reuters.

"The information is tense, let's put it that way, because, yes, there were indeed breakthroughs," the official, Vladimir Saldo told Russian state television.

"There's a settlement called Dudchany, right along the Dnipro River, and right there, in that region, there was a [Ukrainian] breakthrough. There are settlements that are occupied by Ukrainian forces," he continued.

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Russian vehicles destroyed in Ukraine

Destroyed Russian armored vehicles left behind by the Russian forces in Izium, Kharkiv, Ukraine on October 02, 2022. (Photo by Metin Aktas/Anadolu Agency via Getty Images) (getty images)

Destroyed Russian vehicles in Ukraine

Destroyed Russian armored vehicles left behind by the Russian forces in Izium, Kharkiv, Ukraine on October 02, 2022. (Photo by Metin Aktas/Anadolu Agency via Getty Images) (getty images)

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Ukraine has made significant advances in the Dontesk region as well, with Russian troops withdrawing from the key city of Lyman on Friday just hours after Putin claimed to annex the region with a ceremony in Moscow.

The capture grants Ukrainian forces the opportunity to push further into the Luhansk region as well.

Putin held an extravagant event in Moscow to announce Russia's annexing of the Luhansk, Donetsk, Zaporizhzhia and Kherson regions on Friday, declaring the residents there Russian citizens.

The move comes after Russia held widely-criticized referenda in the regions, which found that upward of 87 percent of residents in each region supported Russian rule.

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Russian proxies in the regions claimed to have garnered 87% of civilian support in Kherson, 93% in Zaporizhzhia, 98% in Luhansk and 99% in Donetsk.

Valdimir Putin stands next to Russian military officer at military forum

Russian President Vladimir Putin (left) vows to strengthen Russia's military cooperation with its allies at the Army 2022 International Military and Technical Forum in the Patriot Park outside Moscow, Russia, on Aug. 15, 2022. (Sputnik, Kremlin Pool Photo via AP)

The U.S. and NATO allies have dismissed the so-called votes as "sham referenda" designed to give Putin an excuse for annexation.

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Nevertheless, Putin's move comes amid weeks of success for the Ukrainian military, beginning with an extensive counteroffensive in early September.

Putin was forced to announce a partial military mobilization last month, leading to a surge of military-age men fleeing the country out of fear of being drafted.