KYIV, Ukraine -- Nearly 1,000 last-ditch Ukrainian fighters who had held out inside Mariupol's pulverized steel plant have surrendered, Russia said Wednesday, as the battle that turned the city into a worldwide symbol of defiance and suffering drew toward a close.
Meanwhile, the first captured Russian soldier to be put on trial by Ukraine on war-crimes charges pleaded guilty to killing a civilian and could get life in prison. Finland and Sweden applied to join NATO, abandoning generations of neutrality for fear that Russian President Vladimir Putin will not stop with Ukraine.
The Ukrainian fighters who emerged from the ruined Azovstal steelworks after being ordered by their military to abandon the last stronghold of resistance in the now-flattened port city face an uncertain fate. Some were taken by the Russians to a former penal colony in territory controlled by Moscow-backed separatists.
While Ukraine said it hopes to get the soldiers back in a prisoner swap, Russia threatened to put some of them on trial for war crimes.
Amnesty International said the Red Cross should be given immediate access to the fighters. Denis Krivosheev, Amnesty's deputy director for the region, cited lawless executions allegedly carried out by Russian forces in Ukraine and said the Azovstal defenders "must not meet the same fate."
It was unclear how many fighters remained inside the plant's labyrinth of tunnels and bunkers, where 2,000 were believed to be holed up at one point. A separatist leader in the region said no top commanders had emerged from the steelworks.
The plant was the only thing standing in the way of Russia declaring the full capture of Mariupol. Its fall would make Mariupol the biggest Ukrainian city to be taken by Moscow's forces, giving a boost to Putin in a war where many of his plans have gone awry.
Military analysts, though, said the city's capture at this point would hold more symbolic importance than anything else, since Mariupol is already effectively under Moscow's control and most of the Russian forces that were tied down by the drawn-out fighting have already left.
Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said 959 Ukrainian troops have abandoned the stronghold since they started coming out Monday.
Video showed the fighters carrying out their wounded on stretchers and undergoing pat-down searches before being taken away on buses escorted by military vehicles bearing the pro-Kremlin "Z" sign.
The U.S. has gathered intelligence that shows some Russian officials have become concerned that Kremlin forces in Mariupol are carrying out abuses, including beating and electrocuting city officials and robbing homes, according to a U.S official familiar with the findings.
The Russian officials are concerned that the abuses will further inspire residents to resist the occupation and that the treatment runs counter to Russia's claims that its military has liberated Russian speakers, according to the official, who was not authorized to comment.
In a sign of normalcy returning to Kyiv, the U.S. Embassy reopened on Wednesday, one month after Russian forces abandoned their bid to seize the capital and three months after the outpost was closed. A dozen embassy employees watched solemnly as the American flag was raised.
"The Ukrainian people, with our security assistance, 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," Secretary of State Antony Blinken said in a statement. Other Western countries have been reopening their embassies in Kyiv as well.
In the war-crimes case in Kyiv, Russian Sgt. Vadim Shishimarin, a 21-year-old member of a tank unit, pleaded guilty to shooting an unarmed 62-year-old Ukrainian man in the head through a car window in the opening days of the war. Ukraine's top prosecutor has said some 40 more war-crimes cases are being readied.
On the diplomatic front, Finland and Sweden could become members of NATO in a matter of months, though objections from Turkish President Recep Tayyip Erdogan threaten to disrupt things. Turkey accuses the two countries of harboring Kurdish militants and others it considers a threat to its security.
Ibrahim Kalin, a foreign policy adviser and spokesman for Erdogan, said there will be "no progress" on the membership applications unless Turkey's concerns are met. Each of NATO's 30 countries has an effective veto over new members.
Mariupol's defenders grimly clung to the steel mill for months and against the odds, preventing Russia from completing its occupation of the city and its port.
Its full capture would give Russia an unbroken land bridge to the Crimean Peninsula, which it seized from Ukraine in 2014. It also would allow Russia to focus fully on the larger battle for the Donbas, Ukraine's industrial east.
Rescuers work at a site of an apartment building destroyed by Russian shelling in Bakhmut, Donetsk region, Ukraine, Wednesday, May 18, 2022. (AP Photo/Andriy Andriyenko)
Bodies of dead Russian soldiers lay on the floor during an identification process in Kharkiv, east Ukraine, Tuesday, May 17, 2022. (AP Photo/Bernat Armangue)
Villagers collect scrap metal from a shelled warehouse in the village of Malaya Rohan, Kharkiv region, Wednesday, May 18, 2022. (AP Photo/Bernat Armangue)
Ukrainian servicemen prepare to fire mortars towards Russian positions in east Kharkiv region, Ukraine, Tuesday, May 17, 2022. (AP Photo/Bernat Armangue)
A woman stands next to a destroyed house in Mariupol, in territory under the government of the Donetsk People's Republic, eastern Ukraine, Tuesday, May 17, 2022. (AP Photo/Alexei Alexandrov)
A crater of an explosion is seen after Russian shelling in Soledar, Donetsk region, Ukraine, Wednesday, May 18, 2022. (AP Photo/Andriy Andriyenko)
Rescuers carry the body of a civilian at a site of an apartment building destroyed by Russian shelling in Bakhmut, Donetsk region, Ukraine, Wednesday, May 18, 2022. (AP Photo/Andriy Andriyenko)
Employees of US embassy in Ukraine raise the US national flag at the US embassy, as Russia's attack on Ukraine continues, in Kyiv, Ukraine, Wednesday, May 18, 2022. (AP Photo/Efrem Lukatsky)
NATO Secretary-General Jens Stoltenberg displays documents as Sweden and Finland applied for membership in Brussels, Belgium, Wednesday May 18, 2022. NATO Secretary-General Jens Stoltenberg said that the military alliance stands ready to seize a historic moment and move quickly on allowing Finland and Sweden to join its ranks, after the two countries submitted their membership requests. (Johanna Geron, Pool via AP)