Russian forces have attacked a steel plant in the shattered Ukrainian port city of Mariupol, Ukrainian officials said.
It is an apparent bid to eliminate the last pocket of Ukrainian resistance in the strategic city, the rest of which the Kremlin claims to have seized.
The assault was reported by an adviser to Ukraine's presidential office as an estimated 1,000 civilians sheltered in the Azovstal plant alongside the remaining Ukrainian fighters, while Russian forces pressed their offensive elsewhere in the eastern Donbas region amid fierce Ukrainian counterattacks.
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The presidential adviser, Oleksiy Arestovich, said during a briefing that Russian forces had resumed air strikes on the massive seaside plant and were trying to storm it, which would represent a reversal from an order Russian President Vladimir Putin gave two days earlier.
Russian defence minister Sergei Shoigu told Mr Putin on Thursday that the whole of Mariupol, with the exception of Azovstal, had been "liberated" by the Russians.
At the time, Mr Putin ordered him not to send Russian troops into the plant but instead to block off the facility, an apparent attempt to starve out the Ukrainians and force them to surrender.
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Ukrainian officials have estimated that about 2,000 of their troops are inside the plant along with the civilians sheltering in the facility's underground tunnels. Mr Arestovic said the Ukrainian forces were trying to counter the new attacks.
Both Ukrainian and Russian authorities have said the Azovstal plant is the last remaining defence stronghold in Mariupol, which has strategic importance to Moscow and has been under siege since the start of Russia's invasion of Ukraine.
In Donbas, Russian troops pressed their offensive in an attempt to fully seize Ukraine's industrial heartland but have made little headway as fierce Ukrainian counter-attacks have slowed their efforts, Ukrainian and British officials said.