Russian Foreign Minister Sergey Lavrov announced Tuesday that Moscow is beginning the next stage of its invasion of Ukraine as reports are emerging that the Russian military is conducting a full-scale offensive in the country’s east. 

The ongoing campaign – which Ukrainian President Volodymyr Zelenskyy is calling the "Battle of the Donbas" – comes after Russian forces shifted away from trying to capture the capital, Kyiv. 

"Another stage of this operation [in eastern Ukraine] is beginning and I am sure this will be a very important moment of this entire special operation", Lavrov told the India Today TV Channel, according to Reuters

Ukrainian servicemen ride atop an armored fighting vehicle Tuesday as Russia's attack on Ukraine continues at an unknown location in Eastern Ukraine.

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In a video address overnight, Zelenskyy said a "very large part of the entire Russian army is now focused on this offensive." 

"No matter how many Russian troops they send there, we will fight. We will defend ourselves," he also said. 

A Ukrainian soldier rides atop an armored fighting vehicle in eastern Ukraine on Tuesday. 

Ukrainian security official Oleksiy Danilov said Tuesday that Russian troops are now trying to break through Ukrainian positions "along almost the entire front line of [the] Donetsk, Luhansk and Kharkiv regions," Reuters reported. 

A Ukrainian multiple rocket launcher BM-21 "Grad" shells a Russian troop position near Luhansk in the Donbas region on Sunday. (ANATOLII STEPANOV/AFP via Getty Images)

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New explosions have been heard in the Donetsk region and in the cities of Kharkiv, Mykolaiv and Zaporizhzhia, while air raid sirens could be heard wailing in populated areas near the front line, the news agency also reported, citing officials and local media. 

So far, at least eight people reportedly have been killed and 13 have been wounded in recent fighting in the Luhansk and Donetsk regions.