Ukrainian President Volodymyr Zelenskyy vowed to oppose the Russian offensive in the Donbas region Monday as Russian President Vladimir Putin refocused his forces on the east and south of Ukraine. 

"No matter how many soldiers are drawn there, we will defend ourselves," Zelenskyy said in an address on the results of the 54th day of the war. "We will fight. We will not give up anything Ukrainian."

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In this image from video provided by the Ukrainian Presidential Press Office, Ukrainian President Volodymyr Zelenskyy speaks from Kyiv, Ukraine, Friday, April 8, 2022.

In this image from video provided by the Ukrainian Presidential Press Office, Ukrainian President Volodymyr Zelenskyy speaks from Kyiv, Ukraine, Friday, April 8, 2022. (Ukrainian Presidential Press Office via AP)

"I am grateful to all our fighters, all our heroic cities in Donbas, Mariupol, and the cities of Kharkiv region who hold on," he added. "Which protect the fate of all Ukraine, holding back the strength of the gourd. Rubížne, Popasna, Zolote, Lysyčansk, Sêvierodonetsk, Kramatorsk and all-all, which throughout all these years and forever - with Ukraine."

Russian forces are focusing on the south and east of Ukraine after their initial assault in major cities across the country, most notably the capital of Kyiv, faltered under heavy Ukrainian opposition earlier this month.

Russian forces unleashed a massive artillery and rocket barrage all along Ukraine's eastern front Monday night in what Ukrainian officials say marks the start of a new offensive stretching from Kharkiv in the north to Mariupol in the south. 

"Russian forces have started the battle for the Donbas that they have been getting ready for a long time," Zelenskyy said in a video address Monday. 

Map depicting Ukraine, Russia, Crimea, the Donbas region held by pro-Russian forces, and nearby countries. Ian Jopson, Fox Digital

Map depicting Ukraine, Russia, Crimea, the Donbas region held by pro-Russian forces, and nearby countries. Ian Jopson, Fox Digital. NOTE: Due to scale issues, the borders of Moldova have been stretched – Moldova is a land-locked country. (Fox News)

The Donbas is Ukraine’s mostly Russian-speaking industrial heartland in the east, where Moscow-backed separatists have been fighting Ukrainian forces for the past eight years and have declared two independent republics that have been recognized by Russia.

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In recent weeks, Kremlin declared the capture of the Donbas its main goal of the war after its attempt to storm Kyiv failed.

Ukrainian President Volodymyr Zelenskyy walks in Kyiv.

In this photo provided by the Ukrainian Presidential Press Office, Ukrainian President Volodymyr Zelenskyy, center, walks before a meeting with President of the European Parliament Roberta Metsola in Kyiv, Ukraine, Friday, April 1, 2022.  (Ukrainian Presidential Press Office via AP)