WATCH: Pentagon leadership holds news briefing amid ongoing war in Ukraine

U.S. Department of Defense officials said that as heavy fighting raged Thursday at the shattered steel plant in Mariupol, the majority of Russian forces that were dedicated to Mariupol have left and have moved to the north leaving a small number equivalent of “a couple of battalion tactical groups” still on the ground there.

Watch the briefing in the player above.

Pentagon Press Secretary John Kirby told reporters in a press briefing Thursday, “We still see Mariupol under siege from bombardment through airstrikes predominantly.”

He says that Ukrainian soldiers remain at that plant, and have said they are “still resisting” Russian forces.

Russian forces sought to finish off the city’s last-ditch defenders and complete the capture of the strategically vital Ukrainian port.

The bloody battle came amid growing speculation that President Vladimir Putin wants to present the Russian people with a major battlefield success — or announce an escalation of the war — in time for Victory Day on Monday.

That is the biggest patriotic holiday on the Russian calendar, marking the Soviet Union’s triumph over Nazi Germany.

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Some 2,000 Ukrainian fighters, by Russia’s most recent estimate, were holed up in the tunnels and bunkers under the sprawling Azovstal steelworks in Mariupol, the last pocket of resistance in a city largely reduced to rubble over the past two months.

A few hundred civilians were also believed trapped there.

The Kremlin has demanded the fighters surrender. They have refused. Russia has also accused them of preventing the civilians from leaving.

Meanwhile, 10 weeks into the devastating war, Ukraine’s military claimed it recaptured some areas in the south and repelled other attacks in the east, further frustrating Putin’s ambitions after his abortive attempt to seize Kyiv.

Ukrainian and Russian forces are fighting village by village.

The head of Britain’s armed forces, Chief of the Defense Staff Adm. Tony Radakin, said Putin is “trying to rush to a tactical victory” before Victory Day. But he said Russian forces are struggling to gain momentum in the Donbas.

Kirby said, “In the Donbas region, we would still assess that the Ukrainians are putting up a very stiff resistance and that the Russians have not made the progress that we believe they expected to make by this point.”

He added “I think we would continue to assess it as incremental and uneven, but not non-existent.”