Ukrainian fighters defending the Azovstal steel plant, devastated Mariupol’s last Ukrainian holdout, plan to "stand till the end" as Russian fighters continue their second day of a ground assault on the plant.

The wife of Azov Regiment commander Denys Prokopenko said the fighters "won’t surrender. They only hope for a miracle." 

She said she spoke to her husband on the phone Thursday, and he said he would love her forever. "I am going mad from this," she said. "It seemed like words of goodbye."

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The Ukrainian military's General Staff said Friday that "the blockade of units of the defense forces in the Azovstal area continues" and that the Russians, with aviation support, had resumed assault operations to take control of the sprawling plant.

Smoke rises from the Metallurgical Combine Azovstal in Mariupol, in territory under the government of the Donetsk People's Republic, eastern in Mariupol, Ukraine, Thursday, May 5, 2022. (AP Photo )

The Russians managed to get inside the plant Wednesday with the help of an electrician who knew the layout, said Anton Gerashchenko, an adviser to Ukraine’s Internal Affairs Ministry.

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"He showed them the underground tunnels which are leading to the factory," Gerashchenko said in a video.

In this handout photo taken from video released on Wednesday, May 4, 2022, by Donetsk People's Republic Interior Ministry Press Service, Smoke rises from the Metallurgical Combine Azovstal in Mariupol, in territory under the government of the Donetsk People's Republic, eastern Ukraine.  (Donetsk People's Republic Interior Ministry Press Service via AP)

Russian President Vladimir Putin had initially said forces should just seal off the plant rather than launching a full assault on it and its labyrinth of tunnels, claiming he didn’t want to risk Russian lives unnecessarily, but with Russia’s annual Victory Day celebrations on Monday, experts believe he wants to ramp up the speed in taking the plant. 

But the assault has also come at a "personnel, equipment and munitions" cost to Moscow, a Friday morning update from the U.K. Defense Ministry said. 

FILE - This frame taken from an undated video provided Sunday, May 1, 2022, by the Azov Special Forces Regiment of the Ukrainian National Guard shows people climbing over debris at the Azovstal steel plant, in Mariupol, eastern Ukraine.  (Azov Special Forces Regiment of the Ukrainian National Guard via AP, File)

Putin claimed victory in the city late last month despite Ukrainian fighters remaining inside the plant, refusing to surrender. 

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"Nearly 500 civilians have been evacuated from the Azovstal steel plant in Mariupol," Andriy Yermak, the head of Ukrainian President Volodymyr Zelenskyy’s office, said Friday, according to the Kyiv Independent. Ukraine also said Russia’s continued assaults are preventing the remaining civilians in the plant from escaping. 

"There are many wounded (fighters), but they are not surrendering," Zelenskyy said in his nightly video address. "They are holding their positions." Russia’s latest estimate said there were around 2,000 Ukrainian fighters inside the plant. 

The Pentagon on Thursday said that only about 2,000 Russian soldiers remained around Mariupol with the others moving north and even as Russian airstrikes continue to bombard Mariupol, they are only making "plodding" progress, Pentagon spokesman John Kirby said. 

The Associated Press contributed to this report.