KYIV, May 17 - Mariupol appeared on the verge of falling to the Russians on Tuesday as Ukraine moved to abandon the steel plant where hundreds of its fighters had held out for months under relentless bombardment in the last bastion of resistance in the devastated city.

The capture of Mariupol would make it the biggest city to be taken by Moscow’s forces and would give the Kremlin a badly needed victory, though the landscape has largely been reduced to rubble, The Associated Press reported.

More than 260 Ukrainian fighters — some of them seriously wounded and taken out on stretchers — left the ruins of the Azovstal plant on Monday and turned themselves over to the Russian side in a deal negotiated by the warring parties. An additional seven buses carrying an unknown number of Ukrainian soldiers from the plant were seen arriving at a former penal colony Tuesday in the town of Olenivka, approximately 88 kilometers (55 miles) north of Mariupol.

While Russia called it a surrender, the Ukrainians avoided that word and instead said the plant’s garrison had successfully completed its mission to tie down Russian forces and was under new orders.

“To save their lives. Ukraine needs them. This is the main thing,” Ukrainian Defense Minister Oleksiy Reznikov said.

The Ukrainians expressed hope that the fighters would be exchanged for Russian prisoners of war. But Vyacheslav Volodin, speaker of the lower house of the Russian parliament, said without evidence that there were “war criminals” among the defenders and that they should not be exchanged but tried.

President Volodymyr Zelenskyy said the country’s military and intelligence officers are still working to extract its remaining troops from the sprawling steel mill. Officials have not said how many remain inside.

“The most influential international mediators are involved,” he said.

The operation to abandon the steel plant and its labyrinth of tunnels and bunkers signaled the beginning of the end of a nearly three-month siege that turned Mariupol into a worldwide symbol of both defiance and suffering.

The Russian bombardment killed over 20,000 civilians, according to Ukraine, and left the remaining inhabitants — perhaps one-quarter of the southern port city’s prewar population of 430,000 — with little food, water, heat or medicine.

During the siege, Russian forces launched lethal airstrikes on a maternity hospital and a theater where civilians had taken shelter. Close to 600 people may have been killed at the theater.

Gaining full control of Mariupol would give Russia an unbroken land bridge to the Crimean Peninsula, which it seized from Ukraine in 2014, and deprive Ukraine of a vital port. It could also free up Russian forces to fight elsewhere in the Donbas, the eastern industrial heartland that the Kremlin is bent on capturing.

And it would give Russia a victory after repeated setbacks on the battlefield and the diplomatic front, beginning with the abortive attempt to storm Kyiv, the capital. (ap/ez)