Ukraine said Monday its forces had pushed back Russian troops in the Kharkiv region in a counter-offensive that allowed the Ukrainians to reach the Russian border.
The Ukrainian defense ministry posted a video showing what it said were its troops at the border, with one soldier telling Ukrainian President Volodymyr Zelenskyy, "We are here."
There was no immediate confirmation of the development.
After repelling Russian advances on Kharkiv, Ukraine's second-largest city, Ukrainian forces have regained territory in the region and sought to push Russia from its staging area in Izyum as it focuses on the eastern Donbas region.
"Kremlin dreamed of capturing Kyiv, Kharkiv and Odesa, then at least the Donetsk and Luhansk regions," Zelenskyy adviser Mykhailo Podolyak tweeted Monday. "Now, Russian troops are concentrated on the Luhansk region due to lack of forces. We continue the treatment of imperial megalomania and make Moscow face reality."
Ukrainian servicemen take rest in a recently retaken village north of Kharkiv, east Ukraine, May 15, 2022
Zelenskyy said in a video address late Sunday that Ukraine was preparing for new Russian attacks in the Donbas and southern Ukraine.
"The occupiers still do not want to admit that they are in a dead-end and their so-called 'special operation' has already gone bankrupt," Zelenskyy said.
Russia warned Monday of "far-reaching consequences" if Finland and Sweden join the NATO western military alliance.
Russian news agencies quoted Deputy Foreign Minister Sergei Ryabkov saying the "general level of military tensions will increase," and that the security of Finland and Sweden would not improve.
"They should have no illusions that we will just put up with this," Ryabkov said.
Finland's President Sauli Niinisto and Prime Minister Sanna Marin announced the NATO membership bid Sunday at the presidential palace in Helsinki.
"This is a historic day," Niinisto said. "A new era begins."
A building damaged by multiple shelling stands in Kharkiv, Ukraine, May 15, 2022.
Sweden is also expected to seek entry into the alliance, ending two centuries of military non-alignment. Sweden's governing party on Sunday dropped its opposition to joining NATO.
The two Nordic countries' NATO applications will likely move swiftly, with the alliance's secretary-general, Jens Stoltenberg, saying in recent days that they will be welcomed.
"Finland and Sweden are already the closest partners of NATO," NATO Deputy Secretary-General Mircea Geoana said Sunday in Berlin, where members were meeting to discuss their continued support of Ukraine against Russia's invasion and the expansion of the Atlantic alliance.
Russia cut off electricity to Finland in apparent retaliation for its bid to join NATO. Finland gets 10% of its energy from Russia and the void is now being filled by Sweden.
Turkey initially expressed concerns about Finland and Sweden joining the security alliance, but Saturday said it isn't closing the door on the possibility. Any NATO enlargement requires the unanimous consent of the existing members.
"I'm not that worried," Niinisto said of Turkey's stance.
NATO and the United States said Sunday they both were confident that Turkey would not stand in the way of Finland and Sweden joining NATO. Turkish officials Sunday told foreign ministers in Berlin they want the Nordic countries to halt support for Kurdish militant groups present in their territory, and lift bans on some sales of arms to Turkey.
The top diplomats from the U.S. and Ukraine met Sunday in Berlin to talk about Russia's invasion and the impact it has had not only on Ukraine, but the rest of the world.
U.S. Secretary of State Antony Blinken assured Ukrainian Foreign Minister Dmytro Kuleba of the support that Ukraine has from its allies and discussed this week's Group of Seven industrialized nations and NATO foreign ministerial meetings.
Cindy Saine contributed to this report. Some information for this story came from The Associated Press, Agence France-Presse and Reuters.