Moscow said nearly 700 more Ukrainian fighters had surrendered in Russian-held Mariupol as it shored up a key gain in the south, while the United States became the latest Western country to reopen its embassy in Kyiv.
Ukraine has ordered its garrison in Mariupol to stand down, but the ultimate outcome of Europe's bloodiest battle for decades remains unresolved.
Top commanders of Ukrainian fighters who had made their last stand at the Azovstal steelworks in the port city are still inside the plant, according to the leader of pro-Russian separatists in control of the area, Denis Pushilin, quoted by local news agency DNA on Wednesday.
Ukrainian officials have declined to comment publicly on the fate of the fighters.
"The state is making utmost efforts to carry out the rescue of our service personnel," military spokesman Oleksandr Motuzaynik told a news conference. "Any information to the public could endanger that process."
Ukraine confirmed the surrender of more than 250 fighters on Tuesday but did not say how many more were inside.
Russia said on Wednesday an additional 694 more fighters had surrendered, bringing the total number to 959. Its defence ministry posted videos of what it said were Ukrainian fighters receiving hospital treatment after surrendering at Azovstal.
Ukraine President Volodymyr Zelenskiy, the Red Cross and the United Nations were involved in talks, Mariupol Mayor Vadym Boichenko said, but gave no details.
Mariupol is the biggest city Russia has captured so far and allows Russian President Vladimir Putin to claim a rare victory in the invasion it began on Feb. 24.
Moscow has focussed on the south-east in recent offensives after pulling away from Kyiv, where, in a further sign of normalization, the United States said it had resumed operations at its embassy on Wednesday.
"The Ukrainian people... have defended their homeland in the face of Russia's unconscionable invasion, and, as a result, the Stars and Stripes are flying over the Embassy once again," said U.S. Secretary of State Antony Blinken.
A small number of diplomats would return initially to staff the mission but consular operations will not resume immediately, said embassy spokesperson Daniel Langenkamp.
Canada, Britain and others have also recently resumed embassy operations.
Ukrainian resistance continues in Russian-occupied territory. In the southern city of Melitopol, Ukraine said its fighters, using an explosive device, blew up an armoured train carrying Russian troops.
Reuters could not independently verify the details. Russia's Ministry of Defence did not immediately respond to a request for comment.
Moscow says it is engaged in a "special military operation" to demilitarise and "denazify" its neighbour. The West and Kyiv call that a false pretext for invasion.
Finland and Sweden formally applied for NATO membership on Wednesday, a decision made in the wake of the Ukrainian invasion and the very kind of expansion that Putin cited as a reason for attacking Ukraine.
U.S. Ambassador to NATO Julianne Smith called for an expedited accession process that could be "done in a couple of months", but NATO member Turkey said its approval depended on the return of "terrorists", namely Kurdish militants and Fethullah Gulen followers.
Finland and Sweden were both militarily non-aligned throughout the Cold War.
Although Russia had threatened retaliation against the plans, Putin said on Monday their NATO membership would not be an issue unless the alliance sent more troops or weapons there.
Russia could, however, cut off gas supplies to Finland this week, Finland's state-owned energy provider Gasum said.
The European Commission announced a 210 billion euro ($220 billion) plan for Europe to end its reliance on Russian oil, gas and coal by 2027.
Meanwhile, Google became the latest big Western company to pull out of Russia, saying its local unit had filed for bankruptcy and was forced to shut operations after its bank accounts were seized.
On the battle front, Russian forces continued to press on with their main offensive, trying to capture more territory in the eastern Donbas region which Moscow claims on behalf of separatists.
The capture of Mariupol, the main port for the Donbas, has given Moscow full control of the Sea of Azov and an unbroken swathe of territory across Ukraine's east and south.
The governor of the Luhansk region, part of the Donbas, said there had been a number of attacks there.
"Most of the shelling today was conducted in Severodonetsk and villages nearby... The Russians are still trying to cut the "road of life" through the centre of Luhansk region linking Lysychansk and Bakhmut," Serhity Gaidai wrote on Telegram.