Russia ‘still refitting units’ as more tactical groups arrive, second offensive in Ukraine has yet to begin

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A senior defense official on Tuesday warned that Russia is "still refitting units" and tactical groups continue to enter the country as Moscow looks to target eastern Ukraine.

"They're still refitting units outside of Ukraine for insertion in Ukraine. They have added, over the last 24-hours, another two battalion tactical groups into the country" the senior defense official told reporters, noting there are now 78 operational battalion tactical groups in Ukraine.

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)

RUSSIA LAUNCHES FULL-SCALE OFFENSIVE IN EASTERN UKRAINE, DECLARES 'ANOTHER STAGE' OF WAR HAS STARTED

Defense officials have assessed that Russia has maintained roughly 75 percent of its original combat fighting force from when it first amassed along Ukraine’s borders in the lead up to the invasion. 

Security officials warned that after failing to take the capital city of Kyiv, Moscow would launch a "major offensive" in the eastern regions of Luhansk and Donetsk – also known as the Donbas – where Russian backed separatist forces have been fighting the Ukrainian army since 2014. 

Russian Foreign Minister Sergey Lavrov announced Tuesday that Moscow had begun its second campaign in eastern Ukraine and claimed it will be a "very important moment of this entire special operation."

But a senior U.S. defense official warned that the full campaign has yet to actually kick off. 

"I would say that we have seen some limited offensive operations beginning southwest of Donetsk and south of Izyum. We think that these offensives are preludes to larger offensive operations that the Russians plan to conduct," the official told reporters.

The senior defense official said the U.S. assesses that Russia will attempt to join its forces in the north and south by coming up through Mariupol and down from the Kharkiv area.

Smoke rises above Azovstal steelworks, in Mariupol, Ukraine, in this still image obtained from a recent drone video posted on social media.  (MARIUPOL CITY COUNCIL/via REUTERS  THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT. NO RESALES. NO ARCHIVES.)

RUSSIA SAYS EVACUATION CORRIDORS OPENED FOR MARIUPOL BUT UKRAINE SAYS 4 PEOPLE WERE KILLED TRYING TO FLEE

Despite weeks of intense shelling and attempts to take the strategic port city of Mariupol, U.S. security officials assess that the city is still contested. 

A Mariupol steel plant has become pivotal in the siege as Ukrainian forces and civilians continue to rely on a deep network of tunnels to evade Russian bombardment. 

Over 120,000 residents are believed to still be stuck in the city after Russian forces cut off evacuation points. 

An armed serviceman of Donetsk People's Republic militia walks past a building damaged during fighting in Mariupol on Wednesday. (AP/Alexei Alexandrov)

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The Mariupol mayor estimated that over 20,000 civilians have been killed in the fighting since the invasion began and U.S. defense officials have warned the brutality of the war is expected to escalate as Russia focuses all its effort on an area the size of West Virginia. 

The Biden administration has provided Ukraine with $2.6 billion in defensive aid and the U.S. is expected to deliver another seven flights worth of military aid to Ukraine in next 24 hours.