KYIV, Ukraine — Moscow suffered another diplomatic setback Monday in its war with Ukraine, with Sweden joining Finland in deciding to seek NATO membership, while Ukraine’s president congratulated his soldiers who reportedly pushed back Russian forces near the border.

Sweden’s formal announcement of its intention to join NATO marked a historic shift, ending more than two centuries of military nonalignment.

Swedish Prime Minister Magdalena Andersson warned that the Nordic country would be in a “vulnerable position” during the application period and urged her fellow citizens to brace themselves for the Russian response.

“Russia has said 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.”

Sweden’s move came a day after the governing Social Democratic party endorsed a plan for the country to join the trans-Atlantic alliance, and Finland’s government announced that it would seek to join NATO.

Russian leader Vladimir 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.

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 as terrorists, and of imposing military sanctions on Turkey.

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

Meanwhile, more than 260 Ukrainian fighters, including some 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 Anna Malyar 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.

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

The eastern city of Sievierdonetsk came under heavy shelling, with at least 10 people killed, 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 there.

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

“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.”

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 nations have helped Kyiv hold off or gain ground against Russia, a U.S. defense official said.

The official, who spoke on condition of anonymity to discuss the U.S. military assessment, also 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.

Europe is working to choke off funding for the Kremlin’s war by reducing the billions of dollars it spends on imports of Russian energy.

But a proposed EU embargo faces opposition from some countries dependent on Russian imports, including Hungary, the Czech Republic and Slovakia. Bulgaria also has reservations.