Ukrainian servicemen sit in a bus after leaving Mariupol's besieged Azovstal steel plant, near a penal colony, in Olyonivka. [Source: AP News]

POKROVSK, Ukraine (AP) — Russia claimed to have captured Mariupol on Friday in what would be its biggest victory yet in its war with Ukraine, after a nearly three-month siege that reduced much of the strategic port city to a smoking ruin, with over 20,000 civilians feared dead.

Russian Defense Minister Sergei Shoigu reported to President Vladimir Putin the “complete liberation” of the Azovstal steel plant in Mariupol — the last stronghold of Ukrainian resistance — and the city as a whole, spokesman Igor Konashenkov said.

There was no immediate confirmation from Ukraine.

Russia’s state news agency RIA Novosti quoted the ministry as saying a total of 2,439 Ukrainian fighters who had been holed up at the steelworks had surrendered since Monday, including over 500 on Friday.

As they surrendered, the troops were taken prisoner by the Russians, and at least some were taken to a former penal colony. Others were said to be hospitalized.

The defence of the steel mill had been led by Ukraine’s Azov Regiment, whose far-right origins have been seized on by the Kremlin as part of an effort to cast its invasion as a battle against Nazi influence in Ukraine. Russia said the Azov commander was taken away from the plant in an armoured vehicle.

Russian authorities have threatened to investigate some of the steel mill’s defenders for war crimes and put them on trial, branding them “Nazis” and criminals. That has stirred international fears about their fate.

The steelworks, which sprawled across 11 square kilometres (4 square miles), had been the site of fierce fighting for weeks. The dwindling group of outgunned fighters had held out, drawing Russian airstrikes, artillery and tank fire, before their government ordered them to abandon the plant’s defence and save themselves.

The complete takeover of Mariupol gives Putin a badly needed victory in the war he began on Feb. 24 — a conflict that was supposed to have been a lightning conquest for the Kremlin but instead has seen the failure to take the capital of Kyiv, a pullback of forces to refocus on eastern Ukraine, and the sinking of the flagship of Russia’s Black Sea fleet.

Mariupol endured some of the worst sufferings of the war and became a worldwide symbol of defiance. An estimated 100,000 people remained out of a prewar population of 450,000, many trapped without food, water, heat or electricity. Relentless bombardment left rows upon rows of shattered or hollowed-out buildings.

A maternity hospital was hit by a lethal Russian airstrike on March 9, producing searing images of pregnant women being evacuated from the place. A week later, about 300 people were reported killed in a bombing of a theatre where civilians were taking shelter, although the real death toll could be closer to 600.

Satellite images in April showed what appeared to be mass graves just outside Mariupol, where local officials accused Russia of concealing the slaughter by burying up to 9,000 civilians.

Ukrainian President Volodymyr Zelenskyy said Monday the evacuation of his forces from the miles of tunnels and bunkers beneath Azovstal was done to save the lives of the fighters.

Earlier this month, hundreds of civilians were evacuated from the plant during humanitarian cease-fires and spoke of the terror of ceaseless bombardment, the dank conditions underground and the fear that they wouldn’t make it out alive.