Ukrainian fighters holding the battered Azovstal steel plant through a network of tunnels continued to defy the Russians on Thursday in an increasingly desperate and perhaps doomed effort to deny Moscow what would be its biggest success of the war so far — the complete capture of the strategic port of Mariupol.

The plant remains the last pocket of resistance in Mariupol with around 2,000 fighters as per Russian estiments. The Russian forces began storming the plant earlier this week with civilians still trapped inside, a few hundreds of whom are still believed to be there. A total of 127 civilians were evacuated on Sunday from the plant. Among them, 101 saw daylight after two months of sherltering in the plant.?

The bloody battle at the plant came amid growing speculation that President Vladimir Putin wants to present the Russian people with a battlefield triumph — or announce an escalation of the war — in time for Victory Day on Monday, which is the biggest patriotic holiday on the Russian calendar, marking the Soviet Union's triumph over Nazi Germany in World War Two.

Wife of a Ukrainian commander inside the plant said the fighters are making a last stand. Kateryna Prokopenko, whose husband Denys Prokopenko commands the Azov Regiment inside the plant, told her they will stand till the end.?

Citing her husband, she told AP the defenders will “stand till the end. They only hope for a miracle. They won't surrender".

She said her husband told her he would love her forever. She added, “I am going mad from this. It seemed like words of goodbye.”?

Ukrainian President Volodymyr Zelenskyy said the Russian attack was preventing the evacuation of civilians remaining in the plant's underground bunkers.

He said in his nightly video address, “Just imagine this hell! And there are children there. More than two months of constant shelling, bombing, constant death.”

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

He said, “He showed them the underground tunnels which are leading to the factory. Yesterday, the Russians started storming these tunnels, using the information they received from the betrayer.”

However, The Kremlin denied its troops were storming the plant.

The fall of Mariupol would deprive Ukraine of a vital port, allow Russia to establish a land corridor to the Crimean Peninsula, which it seized from Ukraine in 2014, and free up troops to fight elsewhere in the Donbas region in eastern Ukraine, which is its main objective afer withdrawal from the country's north and area around the capital Kyiv.

Capt. Sviatoslav Palamar, deputy commander of the Azov Regiment, pleaded on Ukrainian TV for the evacuation of civilians and wounded fighters from the steelworks, saying soldiers were “dying in agony due to the lack of proper treatment”.

The Kremlin has demanded the troops surrender, who have refused. Russia has also accused them of preventing the civilians from leaving.

The head of the United Nations said another attempt to evacuate civilians from Mariupol and the plant was underway. UN Secretary-General Antonio Guterres said, “We must continue to do all we can to get people out of these hellscapes."?

But many previous attempts to open safe corridors from Mariupol have fallen through, with Ukraine blaming shelling and firing by the Russians.

(With AP inputs)