KYIV, Ukraine — More than 260 Ukrainian fighters, including some who are badly wounded, were evacuated Monday from a steel plant in the ruined city of Mariupol and taken to areas under Russia’s control, the Ukrainian military said.

Deputy Defense Minister Hanna Maliar said 53 seriously wounded fighters were taken to a hospital in Novoazovsk, east of Mariupol. An additional 211 fighters were evacuated to Olenivka through a humanitarian corridor. An exchange would be worked out for their return home, she said.

Malyar said missions are underway to rescue the remaining fighters inside the plant, the last stronghold of resistance in the devastated southern port city.

“Thanks to the defenders of Mariupol, Ukraine gained critically important time to form reserves and regroup forces and receive help from partners,” she said. “And they fulfilled all their tasks. But it is impossible to unblock Azovstal by military means.”

Ukrainian President Volodymyr Zelenskyy said the evacuation of the fighters from Azovstal to separatist-controlled territory was to save their lives. He said the “heavily wounded” were getting medical help.

“Ukraine needs Ukrainian heroes to be alive. It’s our principle,” he said. “The work continues to bring the guys home, and it requires delicacy and time.”

The steel mill’s defenders got out as Moscow suffered another diplomatic setback in its war with Ukraine, with Sweden joining Finland in deciding to seek NATO membership. And Zelenskyy congratulated soldiers who reportedly pushed Russian forces back near the border.

Earlier Monday, the Russian Defense Ministry announced an agreement for the wounded to leave the steelworks for treatment in a town held by pro-Moscow separatists.

After nightfall Monday, several buses pulled away from the steel mill accompanied by Russian military vehicles.

There was no immediate word on whether the wounded would be considered prisoners of war.

Russian forces pounded targets in the industrial heartland of eastern Ukraine known as the Donbas, and the death toll, already many thousands, kept climbing with the war set to enter its 12th week on Wednesday.

The eastern city of Sievierdonetsk came under heavy shelling that killed at least 10 people, said Serhiy Haidai, the governor of the Luhansk region. In the Donetsk region, Gov. Pavlo Kyrylenko said on Facebook that nine civilians were killed in shelling.

Up to nine explosions were heard west of Lviv, in western Ukraine, and the night sky was lit by an orange glow in the distance. There was no immediate word on what was hit.

But Ukrainian troops also advanced as Russian forces pulled back from around the northeastern city of Kharkiv in recent days. Zelenskyy thanked the soldiers who reportedly pushed all the way to the Russian border in the Kharkiv region in a symbolic gain.

Video showed Ukrainian soldiers carrying a post that resembled a Ukrainian blue-and-yellow-striped border marker. Then they placed it on the ground while a dozen of the soldiers posed next to it, including one with belts of bullets draped over a shoulder.

“I’m very grateful to you, on behalf of all Ukrainians, on my behalf and on behalf of my family,” Zelenskyy said in a video message. “I’m very grateful to all the fighters like you.”

The Ukrainian border service said the video showing the soldiers was from the border “in the Kharkiv region,” but would not elaborate, citing security reasons. It was not immediately possible to verify the exact location.

Ukrainian border guards said they also stopped a Russian attempt to send sabotage and reconnaissance troops into the Sumy region, some 90 miles northwest of Kharkiv.

Russia has been plagued by setbacks in the war, most glaringly in its failure early on to take the capital of Kyiv. Much of the fighting has shifted to the Donbas but also has turned into a slog, with both sides fighting village-by-village.

Howitzers from the U.S. and other countries have helped Kyiv hold off or gain ground against Russia, a senior U.S. defense official said. The official, who spoke on condition of anonymity to discuss the U.S. military assessment, said Ukraine has pushed Russian forces to within a half-mile to 2.5 miles of Russia’s border but could not confirm if it was all the way to the frontier.

The official said Russian long-range strikes also appeared to target a Ukrainian military training center in Yavoriv, near the Polish border. There were no immediate reports of casualties.

The international response to the Russian invasion picked up pace.

Sweden’s decision to seek NATO membership followed a similar decision by neighboring Finland in a historic shift for the counties, which were nonaligned for generations.

Swedish Prime Minister Magdalena Andersson said her country would be in a “vulnerable position” during the application period and urged her fellow citizens to brace themselves.

“Russia has said that that it will take countermeasures if we join NATO,” she said. “We cannot rule out that Sweden will be exposed to, for instance, disinformation and attempts to intimidate and divide us.”

But President Recep Tayyip Erdogan of Turkey, a NATO member, ratcheted up his objection to their joining. He accused the countries of failing to take a “clear” stance against Kurdish militants and other groups that Ankara considers terrorists, and of imposing military sanctions on Turkey.

He said Swedish and Finnish officials who are expected in Turkey next week should not bother to come if they intend to try to convince Turkey of dropping its objection.

“How can we trust them?” Erdogan asked at a joint news conference with the visiting Algerian president.

All 30 current NATO members must agree to let the Nordic neighbors join.

Russian President Vladimir Putin said Moscow “does not have a problem” with Sweden or Finland as they apply for NATO membership, but that “the expansion of military infrastructure onto this territory will of course give rise to our reaction in response.”

Putin launched the invasion on Feb. 24 in what he said was an effort to check NATO’s expansion but has seen that strategy backfire. NATO Secretary-General Jens Stoltenberg has said the membership process for both could be quick.

Europe is also working to choke off funding for the Kremlin’s war by reducing the billions of dollars it spends on imports of Russian energy. A proposed EU embargo faces opposition from some countries dependent on Russian imports, including Hungary, the Czech Republic and Slovakia. Bulgaria also has reservations.

Also Monday, McDonald’s said it has started selling its business in Russia, ending a relationship that has lasted more than three decades. It cited the humanitarian crisis caused by the war, noting that staying in Russia “is no longer tenable, nor is it consistent with McDonald’s values.” The company was the first fast-food restaurant to open in the Soviet Union.